Chrysocolla Chrysocolla Chrysocolla from Nevada, USA General Category Silicate mineral Chemical formula (Cu,Al)2H2Si2O5(OH)4·nH2O Identification Color Blue, blue-green, green Crystal habit Massive, nodular, botryoidal Crystal system Orthorhombic Cleavage none Fracture Brittle to sectile Mohs Scalehardness 2.5 – 3.5 Luster Vitreous to dull Streak white to a blue-green color Diaphaneity Translucent to opaque Specific gravity 1.9 – 2.4 Optical properties Uniaxial (+) Refractive index nω = 1.460 nε = 1.570 Birefringence +0.110 Chrysocolla (hydrated copper silicate) is a mineral, (Cu,Al)2H2Si2O5(OH)4·nH2O. It is of secondary origin and forms in the oxidation zones of copper ore bodies. Associated minerals are quartz, limonite, azurite, malachite, cuprite, and other secondary copper minerals. Chrysocolla has an attractive blue-green colour and is a minor ore of copper, having ahardness of 2.5 to 3.5. It is also used as an ornamental stone. It is typically found as glassybotryoidal or rounded masses and crusts, or vein fillings. Because of its light color, it is sometimes confused with turquoise. Commonly it occurs only as pourous crusts unsuitable for gem use, but high quality, gem grade chrysocolla can be translucent and is highly prized. Chrysocolla Chrysocolla The name comes from the Greek chrysos, “gold”, and kolla, “glue”, in allusion to the name of the material used to solder gold, and was first used by Theophrastus in 315 BCE. Notable occurrences include Israel, Democratic Republic of Congo, Chile, Cornwall inEngland, and Arizona, Utah, New Mexico and Pennsylvania in the United States.

Cerussite

Cerussite
Sample of cerussite-bearing quartzite
General
Category	Carbonate mineral
Chemical formula	Lead carbonate: PbCO3
Identification
Color	Colorless, white, gray, blue, or green
Crystal habit	Massive granular, reticulate, tabular to equant crystals
Crystal system	Orthorhombic – Dipyramidal (2/m 2/m 2/m)
Twinning	Simple or cyclic contact twins
Cleavage	Good [110] and [021]
Fracture	Brittle conchoidal
Mohs Scalehardness	3 to 3.5
Luster	Adamantine, vitreous, resinous
Streak	White
Diaphaneity	Transparent to translucent
Specific gravity	6.53 – 6.57
Optical properties	Biaxial (-)
Refractive index	nα = 1..803 nβ = 2.074 nγ = 2.076
Birefringence	δ = 0.273
Other characteristics	May fluoresce yellow under LW UV
References	[1][2]

Cerussite (also known as lead carbonate or white lead ore) is a mineral consisting of leadcarbonate (PbCO₃), and an importantore of lead. The name is from the Latin cerussa, white lead. Cerussa nativa was mentioned by Conrad Gessner in 1565, and in 1832F. S. Beudantapplied the name cruse to the mineral, whilst the present form, cerussite, is due to W. Haidinger (1845). Miners’ names in early use were lead-spar and white-lead-ore.

Cerussite crystallizes in the orthorhombic system and is isomorphous with aragonite. Like aragonite it is very frequently twinned, the compound crystals being pseudo-hexagonal in form. Three crystals are usually twinned together on two faces of the prism, producing six-rayed stellate groups with the individual crystals intercrossing at angles of nearly 60°. Crystals are of frequent occurrence and they usually have very bright and smooth faces. The mineral also occurs in compact granular masses, and sometimes in fibrous forms. The mineral is usually colorless or white, sometimes grey or greenish in tint and varies from transparent to translucent with an adamantine lustre. It is very brittle, and has a conchoidal fracture. It has aMohs hardness of 3 to 3.75 and a specific gravity of 6.5. A variety containing 7 % of zinc carbonate, replacing lead carbonate, is known as iglesiasite, from Iglesias in Sardinia, where it is found.

The mineral may be readily recognized by its characteristic twinning, in conjunction with the adamantine lustre and high specific gravity. It dissolves with effervescence in dilute nitric acid. A blowpipe test will cause it to fuse very readily, and gives indications for lead.

As crystaline ore

Finely crystallized specimens have been obtained from the Friedrichssegen mine in Lahnsteinnear Nassau, Johanngeorgenstadt inSaxony, Mies in Bohemia, Phoenixville in Pennsylvania,Broken Hill, New South Wales; and several other localities. Delicate acicular crystals of considerable length were found long ago in the Pentire Glaze mine near St Minver in Cornwall. It is often found in considerable quantities, and contains as much as 77.5% of lead.

Lead(II) carbonate is practically insoluble in neutral water (solubility product [Pb²⁺][CO₃^2-] ≈ 1.5×10^-13 at 25 °C), but will dissolve in dilute acids.

Commercial uses

“White lead” is the key ingredient in (now discontinued) lead paints. Ingestion of lead-based paint chips is the most common cause of lead poisoning in children.^[3]

Both “white lead” and lead acetate have been used in cosmetics throughout history, though this practice has ceased in Western countries.^[4]

Serpentine

Serpentine

The serpentine group describes a group of common rock-forming hydrous magnesium ironphyllosilicate ((Mg,Fe)₃Si₂O₅(OH)₄) minerals; they may contain minor amounts of other elements including chromium, manganese, cobalt andnickel. In mineralogy and gemology, serpentine may refer to any of 20 varieties belonging to the serpentine group. Owing to admixture, these varieties are not always easy to individualize, and distinctions are not usually made. There are three important mineral polymorphs of serpentine: antigorite, chrysotile andlizardite.

Overview

“Their olive green color and smooth or scaly appearance is the basis of the name from the Latin serpentinus, meaning serpent rock,” according to Best (2003). They have their origins inmetamorphic alterations of peridotite and pyroxene. Serpentines may also pseudomorphouslyreplace other magnesium silicates. Alterations may be incomplete, causing physical properties of serpentines to vary widely. Where they form a significant part of the land surface, the soil is unusually high in clay.

Antigorite is the polymorph of serpentine that most commonly forms during metamorphism of wet ultramafic rocks and is stable at the highest temperatures—to over 600°C at depths of 60 km or so. In contrast, lizardite and chrysotile typically form near the Earth’s surface and break down at relatively low temperatures, probably well below 400°C. It has been suggested that chrysotile is never stable relative to either of the other two serpentine polymorphs.

Samples of the oceanic crust and uppermost mantle from ocean basins document thatultramafic rocks there commonly contain abundant serpentine. Antigorite contains water in its structure, about 13 percent by weight. Hence, antigorite may play an important role in the transport of water into the earth in subduction zones and in the subsequent release of water to create magmas in island arcs, and some of the water may be carried to yet greater depths.

Soils derived from serpentine are toxic to many plants, because of high levels of nickel,chromium, and cobalt; growth of many plants is also inhibited by low levels of potassium andphosphorus and a low ratio of calcium/magnesium. The flora is generally very distinctive, with specialised, slow-growing species. Areas of serpentine-derived soil will show as strips ofshrubland and open, scattered small trees (often conifers) within otherwise forested areas; these areas are calledserpentine barrens.

Most serpentines are opaque to translucent, light (specific gravity between 2.2–2.9), soft (hardness 2.5–4), infusible and susceptible to acids. All are microcrystalline and massive inhabit, never being found as single crystals. Luster may be vitreous, greasy or silky. Colours range from white to grey, yellow to green, and brown to black, and are often splotchy or veined. Many are intergrown with other minerals, such as calcite and dolomite. Occurrence is worldwide; New Caledonia,Canada (Quebec), USA (northern California), Afghanistan,Cornwall, China, Asia, France, Norway and Italy are notable localities.

Rock composed primarily of these minerals is called serpentinite. Serpentines find use in industry for a number of purposes, such as railway ballasts, building materials, and the asbestiform types find use as thermal and electrical insulation (chrysotile asbestos). The asbestos content can be released to the air when serpentine is excavated and if it is used as a road surface, forming a long term health hazard by breathing. Asbestos from serpentine can also appear at low levels in water supplies through normal weathering processes, but there is as yet no identified health hazard associated with use or ingestion. In its natural state, some forms of serpentine react with carbon dioxide and re-release oxygen into the atmosphere.

The more attractive and durable varieties (all of antigorite) are termed “noble” or “precious” serpentine and are used extensively as gems and in ornamental carvings. Often dyed, they may imitate jade. Misleading synonyms for this material include “Korean jade”, “Suzhou jade”, “Styrian jade”, and “New jade”. New Caledonian serpentine is particularly rich in nickel, and is the source of most of the world’s nickel ore.

Polished slab of bowenite serpentine, a variety of antigorite. Typical cloudy patches and veining are apparent.

The Māori of New Zealand once carved beautiful objects from local serpentine, which they called tangiwai, meaning “tears”. Material quarried in Afghanistan, known as sang-i-yashm, has been used for generations. It is easily carved, taking a good polish, and is said to have a pleasingly greasy feel.

The lapis atracius of the Romans, now known as verde antique, or verde antico, is a serpentinite breccia popular as a decorative facing stone. In classical times it was mined atCasambala, Thessaly, Greece. Serpentinite marbles are also widely used: GreenConnemara marble (or Irish green marble) from Connemara, Ireland (and many other sources), and redRosso di Levanto marble from Italy. Use is limited to indoor settings as serpentinites do not weather well.

Antigorite

Lamellated antigorite occurs in tough, pleated masses. It is usually dark green in color, but may also be yellowish, gray, brown or black. It has a hardness of 3.5–4 and its luster is greasy. The monoclinic crystals show micaceous cleavage and fuse with difficulty. Antigorite is named after its type locality, the Valle di Antigorio in Italy.

Bowenite is an especially hard serpentine (5.5) of a light to dark apple green color, often mottled with cloudy white patches and darker veining. It is the serpentine most frequently encountered in carving and jewellery. The name retinalite is sometimes applied to yellow bowenite. The New Zealand material is called tangiwai.

Although not an official species, bowenite is the state mineral of Rhode Island: this is also the variety’s type locality. A bowenite cabochon featured as part of the “Our Mineral Heritage Brooch”, was presented to First Lady Mrs. Lady Bird Johnson in 1967.

Williamsite is a local varietal name for antigorite that is oil-green with black crystals ofchromite or magnetite often included. Somewhat resembling fine jade, williamsite is cut into cabochons and beads. It is found mainly in Maryland andPennsylvania, USA.^[1]

Lizardite

Polished serpentine, from theVal d’Aosta, sold asGressoney. Used at theUnited Nations building in New York.

Extremely fine-grained, scaly lizardite (also called orthoantigorite) comprises much of the serpentine present in serpentine marbles. It is triclinic, has one direction of perfect cleavage, and may be white, yellow or green. Lizardite is translucent, soft (hardness 2.5) and has an average specific gravity of 2.57. It can be pseudomorphous after enstatite,olivine or pyroxene, in which case the name bastite is sometimes applied. Bastite may have a silky lustre.

Lizardite is named after its type locality on the Lizard Peninsula, Cornwall, UK.^[2] It is worked by local artisans into various trinkets which are sold to tourists.

The California State Rock is Serpentinite.

Onyx This article is about the mineral. For other uses, see Onyx (disambiguation). Onyx is a cryptocrystalline form of quartz. The colors of its bands range from white to almost every color (save some shades, such as purple or blue). Commonly, specimens of onyx available contain bands of colors of white, tan, and brown.Sardonyx is a variant in which the colored bands are sard (shades of red) rather than black. Pure black onyx is common, and perhaps the most famous variety, but not as common as onyx with banded colors. Sardonyx (banded agate). The specimen is 2.5 cm (1 inch) wide. It is usually cut as a cabochon, or into beads, and is also used for intaglios and cameos, where the bands make the image contrast with the ground. Some onyx is natural but much is produced by the staining of agate. The name has sometimes been used, incorrectly, to label other banded lapidary materials, such as banded calcite found inMexico, Pakistan, and other places, and often carved, polished and sold. This material is much softer than true onyx, and much more readily available. The majority of carved items sold as ‘onyx’ today are this carbonate material.[1] Technical details Chemical composition and name SiO2 - Silicon dioxide Hardness (Mohs scale) 7 Specific gravity 2.65 – 2.667 Refractive index (R.I.) 1.543 – 1.552 to 1.545 – 1.554 Birefringence 0.009 Optic sign Positive Optical character Uniaxial Etymology Onyx comes through Latin from the Greek onyx meaning ‘claw’ or ‘fingernail’. With its fleshtone color, onyx can be said to resemble a fingernail. The English word ‘nail’ is cognatewith the Greek word.[2] Historical usage Onyx from Australia. Onyx from Brazil. The Beinecke Rare Book and Manuscript Library at Yale University was originally planned to be coated in green onyx. However, there wasn’t sufficient green onyx in the world to build such a structure, so that the designers used marble. Onyx was known to the ancient Greeks and Romans.[3] Use of sardonyx appears in the art of Minoan Crete, notably from the archaeological recoveries at Knossos.[4] Onyx was used in Egypt as early as the Second Dynasty to make bowls and other pottery items.[5] It is also mentioned in Exodus 25. Black onyx with bands of colors.

Tufa

Tufa towers at Mono Lake, California.

Tufa forming the Trona Pinnacles, California.

Tufa (sometimes also known as sinter) is a soft, friable and porous calcite rock. It is acalcium carbonate (CaCO₃) deposit that forms by chemical/biological precipitation from bodies of water with a high dissolved calcium content. Calcareous tufa is not to be confused with tuff, a hard volcanic rock that is also sometimes called tufa.

Tufa deposition occurs in seven known ways:

1. Mechanical precipitation by wave action against the shore. This form of tufa can be useful for identifying the shoreline of extinct lakes (for example in the Lake Lahontanregion).
2. Precipitation from supersaturated hot spring water entering cooler lake water.
3. Precipitation in lake bottom sediments which are fed by hot springs from below.
4. Precipitation from calcium-bearing spring water flowing into an alkaline lake.
5. Precipitation throughout a lake as the lake water evaporates, leaving the lake supersaturated in calcium.
6. Through the agency of algae. Microbial influence is often vital to tufa precipitation and may be involved in the other methods listed.
7. Precipitation from cold water springs (for example in the foothills of the Rocky Mountains near Hinton, Alberta).

Tufa is common in many parts of the world. There are some prominent towers of tufa at Mono Lake and Trona Pinnacles in California, USA, formed by the fourth method mentioned above whilst submerged and subsequently exposed by falling water levels. Tufa is also common inArmenia and Great Britain.

Practical use

Tufa is today occasionally shaped into a planter. Its porous consistency makes tufa ideal foralpine gardens. A concrete mixture called hypertufa is used for similar purposes.

Orbicular jasper

Orbicular jasper from Madagascar

Orbicular jasper is a variety of jasper which contains variably-colored orbs or spherical inclusions or zones. In highly silicifiedrhyolite or tuff, quartz and feldspar crystallize in radial aggregates of needle-like crystals which provide the basis or seed for the orbicular structure seen in this kind of jasper[1]. The material is quite attractive when polished and is used as an ornamental stone orgemstone.

Various local or commercial names have been used for the material, such as kinradite, oregonite, owyhee jasper, ocean jasper and poppy-patterned jasper, depending on the source.Poppy-patterned jasper or Poppy jasper is the varietal name for material fromMorgan Hill,Santa Clara County, California. The trade name ocean jasper is used for a variety found along the intertidal shores of northeast Madagascar. In Nebraska orbicular jasper is found in altered rhyolite beds noted for a variety of jaspers and related agates.

Coral Coral Pillar coral, Dendrogyra cylindricus Scientific classification Kingdom: Animalia Phylum: Cnidaria Class: Anthozoa Ehrenberg, 1831 Extant Subclasses and Orders Alcyonaria Alcyonacea Helioporacea Zoantharia Antipatharia Corallimorpharia Scleractinia Zoanthidea [1][2] See Anthozoa for details Corals are marine organisms from the class Anthozoa and exist as small sea anemone-like polyps, typically in colonies of many identical individuals. The group includes the important reef builders that are found in tropical oceans, which secretecalcium carbonate to form a hard skeleton. A coral “head”, commonly perceived to be a single organism, is formed from myriads of individual but genetically identicalpolyps, each polyp only a few millimeters in diameter. Over thousands of generations, the polyps lay down a skeleton that is characteristic of their species. An individual head of coral grows by asexual reproduction of the individual polyps. Corals also breed sexually by spawning, with corals of the same species releasing gametes simultaneously over a period of one to several nights around a full moon. Although corals can catch small fish and animals such as plankton using stinging cells on their tentacles, these animals obtain most of their nutrients from photosynthetic unicellular algae called zooxanthellae. Consequently, most corals depend on sunlight and grow in clear and shallow water, typically at depths shallower than 60 m (200 ft). These corals can be major contributors to the physical structure of the coral reefs that develop in tropical and subtropical waters, such as the enormous Great Barrier Reef off the coast of Queensland, Australia. Other corals do not have associated algae and can live in much deeper water, with the cold-water genus Lophelia surviving as deep as 3000 m.[3] Examples of these can be found living on the Darwin Mounds located north-west of Cape Wrath, Scotland. Corals have also been found off the coast ofWashington State and the Aleutian Islands in Alaska. Corals coordinate behaviour by communicating with each other.[4] Phylogeny A Short Tentacle Plate coralinPapua New Guinea Main article: Anthozoa Corals belong to the class Anthozoa and are divided into two subclasses, depending on the number of tentacles or lines of symmetry, and a series of orders corresponding to their exoskeleton, nematocyst type and mitochondrial genetic analysis.[1][2][5] Those with eight tentacles are called octocorallia or Alcyonariaand comprise soft corals, sea fans and sea pens. Those with more than eight in a multiple of six are called hexacorallia or Zoantharia. This group includes reef-building corals (Scleractinians), sea anemones andzoanthids. Anatomy Anatomy of a coral polyp While a coral head appears to be a single organism, it is actually a head of many individual, yet genetically identical, polyps. The polyps are multicellular organisms that feed on a variety of small organisms, from microscopic plankton to small fish. Polyps are usually a few millimeters in diameter, and are formed by a layer of outer epithelium and inner jellylike tissue known as the mesoglea. They are radially symmetrical with tentacles surrounding a central mouth, the only opening to the stomach or coelenteron, through which both food is ingested and waste expelled. The stomach closes at the base of the polyp, where the epithelium produces an exoskeleton called the basal plate or calicle (L. small cup). This is formed by a thickened calciferous ring (annular thickening) with six supporting radial ridges (as shown below). These structures grow vertically and project into the base of the polyp. When polyps are physically stressed, they contract into the calyx so that virtually no part is exposed above the skeletal platform. This protects the organism from predators and the elements (Barnes, R.D., 1987; Sumich, 1996).[6][7] The polyp grows by extension of vertical calices which are occasionally septated to form a new, higher, basal plate. Over many generations this extension forms the large calciferous (Calcium containing) structures of corals and ultimately coral reefs. Formation of the calciferous exoskeleton involves deposition of the mineral aragonite by the polyps fromcalcium ions they acquire from seawater. The rate of deposition, while varying greatly across species and environmental conditions, can be as much as 10 g / m² of polyp / day (0.3 ounce / sq yd / day). This is light dependent, with night-time production 90% lower than that during the middle of the day.[8] Nematocyst discharge: A dormant nematocyst discharges response to nearby prey touching the cnidocil, the operculum flap opens and its stinging apparatus fires the barb into the prey leaving a hollow filament through which poisons are injected to immobilise the prey, then the tentacles manoeuvre the prey to the mouth. The polyp’s tentacles trap prey using stinging cells called nematocysts. These are cells modified to capture and immobilize prey, such as plankton, by injecting poisons, firing very rapidly in response to contact. These poisons are usually weak but in fire corals are potent enough to harm humans. Nematocysts can also be found in jellyfish and sea anemones. The toxins injected by nematocysts immobilize or kill prey, which can then be drawn into the polyp’s stomach by the tentacles through a contractile band of epithelium called the pharynx. The polyps interconnect by a complex and well developed system of gastrovascular canals allowing significant sharing of nutrients and symbiotes. In soft corals these range in size from 50-500 μm in diameter and to allow transport of both metabolites and cellular components.[9] Close-up of Montastrea cavernosa polyps. Tentacles are clearly visible. Aside from feeding on plankton, many corals as well as other cnidarian groups such as sea anemones (e.g.Aiptasia), form asymbiotic relationship with a class of algae, zooxanthellae, of the genus Symbiodinium. The sea anemone Aiptasia, while considered a pest among coral reef aquarium hobbyists, has served as a valuable model organism in the scientific study of cnidarian-algal symbiosis. Typically a polyp harbors one particular species of algae. Via photosynthesis, these provide energy for the coral, and aid in calcification.[10] The algae benefit from a safe environment, and use the carbon dioxide and nitrogenous waste produced by the polyp. Due to the strain the algae can put on the polyp, stress on the coral often triggers ejection of the algae, known on a large scale as coral bleaching, as it is the algae that contribute to the brown coloration of corals; other colors, however, are due to host coral pigments, such as GFPs (green fluorescent protein). Ejecting the algae increases the polyps’ chances of surviving stressful periods – they can regain the algae at a later time. If the stressful conditions persist, the corals eventually die.[11] Reproduction Corals can be both gonochoristic (unisexual) and hermaphroditic, each of which can reproduce sexually and asexually. Reproduction also allows coral to settle new areas. Sexual Life cycles of broadcasters and brooders. Corals predominantly reproduce sexually, with 25% of hermatypic corals (stony corals) forming single sex (gonochoristic) colonies, whilst the rest are hermaphroditic.[12] About 75% of all hermatypic corals “broadcast spawn” by releasing gametes – eggs and sperm – into the water to spread offspring over large distances. The gametes fuse during fertilisation to form a microscopic larvum called a planula, typically pink and elliptical in shape; a moderately sized coral colony can form several thousands of these larvae per year to overcome the huge odds against formation of a new colony.[13] The planula swims towards light, exhibiting positive phototaxis, to surface waters where they drift and grow for a time before swimming back down to locate a surface on which it can attach and establish a new colony. At many stages of this process there are high failure rates, and even though millions of gametes are released by each colony very few new colonies form. The time from spawning to settling is usually 2 or 3 days, but can be up to 2 months.[14] The larva grows into a coral polyp and eventually becomes a coral head by asexual budding and growth, creating new polyps. A male star coral, Montastraea cavernosa, releases sperm into the water. Corals that do not broadcast their eggs are called brooders, this is the case for most non-stony corals. These corals release sperm but harbour eggs, allowing larger, negatively buoyant, planulae to form which the polyp later releases ready to settle.[10] The larva grows into a coral polyp and eventually becomes a coral head by asexual budding. Synchronous spawning is very typical on a coral reef and often, even when multiple species are present, all the corals on the reef release gametes the same night. This synchrony is essential so that male and female gametes can meet and form planula. The cues that guide the release are complex, but over the short term involve lunar changes, sunset time, and possibly chemical signalling.[12] Synchronous spawning may have the result of forming coral hybrids and is perhaps involved in coral speciation.[15] In some places the coral spawn can be dramatic, usually occurring at night, where the usually clear water becomes cloudy with gametes. Corals must rely on environmental cues, varying from species to species, to determine the proper time to release gametes into the water. Corals use two methods for sexual reproduction, which differ in whether the female gametes are released: Broadcasters, the majority of which mass spawn, rely heavily on environmental cues, because in contrast to brooders they release both sperm and eggs into the water. The corals use long-term cues such as day length, water temperature, and/or rate of temperature change. The short-term cue is most often the lunar cycle, with the sunset cuing the time of release.[12] About 75% of coral species are broadcasters, the majority of which are hermatypic, or reef-building corals.[12] The positively buoyant gametes float towards the surface where fertilization occurs to produce planulalarvae. The planula larvae swim towards the surface light to enter into currents, where they remain usually for two days, but can be up to three weeks, and in one known case two months,[14] after which they settle and metamorphose into polyps and form colonies. Brooders are most often ahermatypic (non-reef building) in areas of high current or wave action. Brooders release only sperm, which is negatively buoyant, and can store unfertilized eggs for weeks, lowering the need for mass synchronous spawning events, which do sometimes occur.[12] After fertilization the corals release planula larvae which are ready to settle. Asexual Calices (basal plates) ofOrbicella annularisshowing two methods of multiplication: gemmation (small central calicle) and division (large double calicle). Within a coral head the genetically identical polyps reproduce asexually to allow colony growth. This is achieved either through gemmation (budding) or through division, both shown in the diagrams of Orbicella annularis. Budding involves a new polyp growing from an adult, whereas division forms two polyps each as large as the original.[13] Budding expands the size of a coral colony. It occurs when a new corallite grows out from the adult polyp. As the new polyp grows it produces a coelenteron (stomach), tentacles and a mouth. The distance between the new and adult polyps grows, and with it the coenosarc (the common body of the colony; see coral anatomy). Budding can occur by means of: Intra-tentacular budding forms from the oral discs of a polyp, meaning that both polyps are the same size and are within the same ring of tentacles. Extra-tentacular budding forms from the base of a polyp, and the new polyp is smaller. Longitudinal division begins with broadening of a polyp, which then divides the coelenteron. The mouth divides and new tentacles form. The two “new” polyps must generate their missing body parts and exoskeleton.. Transversal division occurs when polyps and the exoskeleton divide transversally into two parts. This means that one has the basal disc (bottom) and the other has the oral disc (top). The two new polyps must again generate the missing parts. Fission occurs in some corals, especially among the family Fungiidae, where the colony is able to split into two or more colonies during the early stages of their development. Whole colonies can reproduce asexually through fragmentation or bailout, forming another individual colony with the same genome.. Polyp bailout occurs when a single polyp abandons the colony and re-establishes on a new substrate to create a new adult colony.. Fragmentation, involves individuals broken from the colony during storms, or other situations where breaking can occur. The separated individuals can start new coral colonies. Reefs Locations of coral reefs Main article: Coral reef The hermatypic, stony corals are often found in coral reefs, large calcium carbonate structures generally found in shallow,tropical water. Reefs are built up from coral skeletons and held together by layers of calcium carbonate produced bycoralline algae. Reefs are extremely diverse marine ecosystems being host to over 4,000 species of fish, massive numbers of cnidarians, mollusks, crustaceans, and many other animals.[16] Types Hermatypic corals Further information: Scleractinia Further information: Millepora Further information: Tubipora Further information: Heliopora Hermatype corals or stony corals build reefs. With the help of zooxanthellae, they convert surplus food to calcium carbonate forming a hard skeleton. Hermatype-species include Scleractinia, Millepora, Tubiporaand Heliopora. [17] In the Caribbean alone 50 species of uniquely structured hard coral exist. Some of the most well known types being: Brain coral grow to 1.8 meters in width. Acropora and Staghorn coral grow fast and large and are important reef-builders. Staghorn coral displays large antler-like branches and grows in areas with strong surf. Galaxea fascicularis or star coral is another important reef-builder. Pillar coral forms pillars which can grow to 3 meters in height.. Leptopsommia or rock coral, appears almost everywhere in the Caribbean[18]. Ahermatypic corals Further information: Alcyonacea Further information: Anthipatharia Ahermatypic corals are corals that have no zooxanthellae and can therefore not build the solid skeletons that form reefs. They include Alcyonaceas, as well as some Anthipatharia-species (Black coral, Cirripathes,Antipathes). [17] Ahermatypic corals such as sea whips, sea feathers, and sea pens [18] are also known as soft corals. Unlike stony corals, they are flexible, moving back and forth in the current, and often are perforated, with a lace-like appearance. Their skeletons are made of protein, rather than calcium. Soft corals are somewhat less plentiful (in the Caribbean, twenty species appear) than stony corals. Evolutionary history The fossil coral Heliophyllum hallifrom the Devonian period, found inCanada. Although corals first appeared in the Cambrian period,[19] some 542 million years ago, fossils are extremely rare until theOrdovician period, 100 million years later, when Rugose and Tabulate corals became widespread. Tabulate corals occur in the limestones and calcareous shales of the Ordovician and Silurian periods, and often form low cushions or branching masses alongside Rugose corals. Their numbers began to decline during the middle of the Silurian period and they finally became extinct at the end of the Permian period, 250 million years ago. The skeletons of Tabulate corals are composed of a form of calcium carbonate known as calcite. Rugose corals became dominant by the middle of the Silurian period, and became extinct early in theTriassic period. The Rugose corals existed in solitary and colonial forms, and are also composed of calcite. The Scleractinian corals filled the niche vacated by the extinct Rugose and Tabulate species. Their fossils may be found in small numbers in rocks from the Triassic period, and become relatively common in theJurassic and later periods. Scleractinian skeletons are composed of a form of calcium carbonate known asaragonite.[20] Although they are geologically younger than the Tabulate and Rugose corals, their aragonitic skeleton is less readily preserved, and their fossil record is less complete.. Timeline of the major coral fossil record and developments from 650 m.y.a. to present.[21][22] edit At certain times in the geological past corals were very abundant. Like modern corals, these ancestors built reefs, some of which now lie as great structures in sedimentary rocks. Fossils of fellow reef-dwellers algae, sponges, and the remains of many echinoids, brachiopods, bivalves,gastropods, andtrilobites appear along with coral fossils. This makes some corals useful index fossils, enabling geologists to date the age the rocks in which they are found. Coral fossils are not restricted to reef remnants, and many solitary corals may be found elsewhere, such asCyclocyathus, which occurs in England‘s Gault clay formation. Environmental influences A healthy coral reef has a striking level of biodiversity in many forms of marine life. Corals are highly sensitive to environmental changes. Scientists have predicted that over 50% of the world’scoral reefs may be destroyed by the year 2030;[23] as a result most nations protect them through environmental laws. Algae can overwhelm a coral reef if too many nutrients are present. Coral will also die if the water temperature changes by more than a degree or two beyond its normal range or if the salinity of the water drops. In an early symptom of environmental stress, corals expel their zooxanthellae; without their symbiotic unicellular algae, coral tissues become colorless as they reveal the white of their calcium carbonate skeletons, an event known as coral bleaching.[24] Many governments now prohibit removal of coral from reefs and use education to inform their populations about reef protection and ecology. However, many other human activities damage reefs, including mooring, fishing, diving, mining and construction. The narrow niche that coral occupies, and the stony corals‘ reliance on calcium carbonate deposition, means they are susceptible to changes in water pH. The increase in atmospheric carbon dioxide has caused enough dissolution of carbon dioxide to lower the ocean’s pH, in a process known as ocean acidification. Lowered pH reduces the ability of corals to produce calcium carbonate, and at the extreme, can entirely dissolve those skeletons. Without deep and immediate cuts in anthropogenic CO2 emissions, scientists fear that ocean acidification will result in the severe degradation or destruction of coral species and ecosystems.[25] A section through a coral, dyed to determine growth rate Climatic variations can cause temperature changes that destroy corals. For example, during the 1997-98 warming event all the hydrozoan Millepora boschmai colonies near Panamá were bleached and died within six years – this species is now thought to be extinct.[26] Uses Live corals Local economies near major coral reefs benefit from an abundance of fish and other marine creatures as a food source. Reefs also provide recreational scuba diving and snorkeling tourism. Unfortunately these activities can also have deleterious effects, such as accidental destruction of coral. Coral is also useful as a protection against hurricanes and other extreme weather. Live coral is highly sought after in the aquarium trade. Provided the proper ecosystem, live coral makes a stunning addition to any salt water aquarium. Soft corals are considered easier to maintain in captivity than hard corals.[27] Deep sea bamboo corals (Isididae) may be among the first organisms to display the effects of ocean acidification. They produce growth rings similar to those of tree and can provide a view of changes in the condition in the deep sea over time.[28] Other coral biology research presents the possibility that Isididae corals, because of their potential to mimic biological properties, may be usable as living bone implants and in aquatic cultivation.[29] Coral as a gemstone Main article: Coral (precious) Intensely red coral is sometimes called fire coral (but this is not at all the same thing as fire coral). Red coral is very rare now because of overharvesting due to the great demand for perfect red coral in jewelry-making. Ancient corals Tabulate coral (a syringoporid); Boone Limestone (LowerCarboniferous) near Hiwasse, Arkansas. Scale bar is 2.0 cm. Ancient coral reefs on land are often mined for lime or use as building blocks (“coral rag“). Coral rag is an important local building material in places such as the East African coast. The annual growth bands in bamboo corals and others allow geologists to construct year-by-year chronologies, a form ofincremental dating, which can provide high-resolution records of past climatic andenvironmental changes usinggeochemical techniques.[30] Certain species of corals form communities called microatolls. The vertical growth of microatolls is limited by average tidal height. By analyzing the various growth morphologies, microatolls can be used as a low resolution record of patterns of sea level change. Fossilized microatolls can also be dated using radioactive carbon dating. Such methods have been used to used to reconstruct Holocene sea levels.[31] Gallery Further images: commons:Category:Coral reefs and commons:Category:Coral Fungia sp. skeleton Brain coral, Diploria labyrinthiformis Polyps of Eusmilia fastigiata Staghorn coral,Acropora Orange cup coral,Balanophyllia elegans Brain coral spawning Brain coral releasing eggs Fringing coral reef off the coast of Eilat, Israel.

Rhodochrosite

Rhodochrosite
Rhodochrosite from Sweet Home Mine, Alma, Colorado, USA
General
Category	Mineral species
Chemical formula	MnCO3
Identification
Molar mass	114.95 g/mol
Color	Red to pink, Brown to yellow, gray to white
Crystal habit	Massive to well crystaline
Crystal system	Trigonal -HexagonalScalenohedral
Twinning	on the {0112} uncommon
Cleavage	on the [1011] perfect
Fracture	uneven, conchoidal
Tenacity	brittle
Mohs Scalehardness	3.5-4
Luster	Vitreous
Streak	White
Diaphaneity	Transparent to translucent
Density	3.7 g/cm³
Optical properties	Uniaxial (-)
Birefringence	δ = 0.218
Pleochroism	weak
Ultravioletfluorescence	None

Pink is the most common color of Rhodochrosite. Specimen mined near Silverton, Colorado

Rhodochrosite is a manganese carbonate mineral with chemical composition MnCO₃. In its (rare) pure form, it is typically a rose-red color, but impure specimens can be shades of pink to pale brown. The streak is white. Its Mohs hardness varies between 3.5 and 4. Its specific gravity is 3.5 to 3.7. It crystallizes in the trigonal system. The cleavage is typical rhombohedral carbonate cleavage in three directions. Crystal twinning often is present. It is transparent to translucent with refractive indices of nω=1.814 to 1.816,nε=1.596 to 1.598. It is often confused with the manganese silicate, rhodonite, but is distinctly softer.

Rhodochrosite forms a complete solid solution series with iron carbonate (siderite). Calcium, (as well as magnesium and zinc, to a limited extent) frequently substitutes for manganese in the structure, leading to lighter shades of red and pink, depending on the degree of substitution. It is for this reason that the most common color encountered is pink.

Rhodochrosite occurs as a hydrothermal vein mineral along with other manganese minerals in low temperature ore deposits as in the silver mines of Romania where it was first found. Banded rhodochrosite is mined in Capillitas, Argentina. Catamarca, Argentina has an old Incan silver mine that has produced fine stalactitic examples of rhodochrosite that are unique and very attractive. Cut cross-sections reveal concentric bands of light and dark rose colored layers.. These specimens are carved and used for many ornamental purposes.^[3]

Its main use is as an ore of manganese which is a key component of low-cost stainless steel formulations and certain alluminium alloys. Quality banded specimens are often used for decorative stones and jewelry. Due to its being relatively soft, and having perfect cleaveage, it is very difficult to cut, and therefore rarely found faceted in jewelry.

It was first described in 1813 in reference to a sample from Cavnic, Maramureş, present-dayRomania. According to Dimitrescu and Radulescu, 1966 and to Papp, 1997, this mineral was described for the first time in Sacaramb, Romania, not in Cavnic, Romania. The name is derived from the Greek word for rose-colored.

Colorado officially named rhodochrosite as its state mineral in 2002 based on a proposal by a local high school (Platte Canyon High School in Bailey,Colorado). The reason for this lies in the fact that while the mineral is found worldwide, large red crystals are found only in a few places on earth, and some of the best specimens have been found in the Sweet Home Mine near Alma, Colorado.

The Alma King is the largest known rhodochrosite crystal; it was found in theSweet Home Mine near Alma, Colorado. It is on display in the Denver Museum of Nature and Science.

The Incas believed that rhodochrosite is the blood of their former rulers, turned to stone, therefore it is sometimes called “Rosa del Inca” or “Inca Rose”.^[4][5]

Rhodochrosite and silver mining

Manganese carbonate is extremely destructive to the amalgamation process used in the concentration of silver ores, and so until quality mineral specimens became highly sought after by collectors, they

Labradorite

Labradorite
Labradorite
General
Category	feldspar, tectosilicate
Chemical formula	(Ca,Na)(Al,Si)4O8, whereCa/(Ca + Na) (%Anorthite) is between 50%-70%
Identification
Crystal system	triclinic
Twinning	common
Cleavage	three directions
Streak	white
Specific gravity	2.71 to 2.74
Refractive index	1.555 to 1.575
Other characteristics	iridescence

Detail of Labradorite

Labradorite ((Ca,Na)(Al,Si)₄O₈), a feldspar mineral, is an intermediate to calcic member of the plagioclase series. It is usually defined as having “%An” (anorthite) between 50 and 70. The specific gravity ranges from 2.71 to 2.74. The streak is white, like most silicates. Therefractive index ranges from 1.555 to 1.575. Twinning is common. As with all plagioclase members the crystal system is triclinic and three directions of cleavage are present two of which form nearly right angle prisms. It occurs as clear, white to gray, blocky to lath shaped grains in common mafic igneous rocks such as basalt and gabbro, as well as in anorthosites.

The geological type area for labradorite is Paul’s Island near the town of Nain in Labrador,Canada. It occurs in large crystal masses in anorthosite and shows an iridescence or play of colors. The iridescence is the result of light refracting within lamellar intergrowths resulting from phase exsolution on cooling in the Boggild miscibility gap, An₄₈-An₅₈.

Gemstone varieties of labradorite exhibiting a high degree of iridescence are called spectrolite;moonstone and sunstone are also commonly used terms, and high-quality samples with good iridescent qualities are desired for jewelry

Feldspar

feldspar
Potassium feldspar crystals in a granite, eastern Sierra Nevada, Rock Creek Canyon, California. Scale bar is 2.0 cm.
General
Category	tectosilicate
Chemical formula	KAlSi3O8 - NaAlSi3O8-CaAl2Si2O8
Identification
Color	pink, white, gray, brown
Crystal system	triclinic or monoclinic
Twinning	tartan, carlsbad, etc
Cleavage	three
Fracture	along cleavage planes
Mohs Scalehardness	6
Luster	vitreous
Diaphaneity	opaque
Birefringence	first order
Pleochroism	none
Other characteristics	exsolution lamellae common

This article is about a mineral. For the Malcolm in the Middle character, see List of characters in Malcolm in the Middle#Recurring characters.

Lunar Ferroan Anorthosite #60025 (Plagioclase Feldspar). Collected by Apollo 16 from the Lunar Highlands nearDescartes Crater. This sample is currently on display at the National Museum of Natural Historyin Washington, DC, United States. (Unknown scale.)

Feldspars (KAlSi₃O₈ - NaAlSi₃O₈ - CaAl₂Si₂O₈) are a group of rock-forming tectosilicateminerals which make up as much as 60% of the Earth‘s crust.^[1]

Feldspars crystallize from magma in both intrusive and extrusive igneous rocks, as veins, and are also present in many types ofmetamorphic rock.^[2] Rock formed entirely of plagioclasefeldspar (see below) is known as anorthosite.^[3] Feldspars are also found in many types ofsedimentary rock.^[4]

Etymology

Feldspar is derived from the German Feld, field, and Spat, a rock that does not contain ore. “Feldspathic” refers to materials that contain feldspar. The alternative spelling, felspar, has now largely fallen out of use.^[5]

Compositions

Compositional phase diagram of the different minerals that constitute the feldspar solid solution.

Feldspar.

Alkali feldspar perthite (7cm long X 3cm width).

This group of minerals consists of framework or tectosilicates. Compositions of major elements in common feldspars can be expressed in terms of three endmembers:

Potassium-Feldspar (K-spar) endmember KAlSi₃O₈^[1]

Albite endmember NaAlSi₃O₈^[1]

Anorthite endmember CaAl₂Si₂O₈^[1]

Solid solutions between K-feldspar and albite are called alkali feldspar.^[1] Solid solutions between albite and anorthite are calledplagioclase,^[1] or more properly plagioclase feldspar. Only limited solid solution occurs between K-feldspar and anorthite, and in the two other solid solutions, immiscibility occurs at temperatures common in the crust of the earth. Albite is considered both a plagioclase and alkali feldspar. In addition to albite, barium feldspars are also considered both alkali and plagioclase feldspars. Barium feldspars form as the result of the replacement of potassium feldspar.

Alkali Feldspars

The alkali feldspars are as follows:

• orthoclase (monoclinic),^[6] — KAlSi₃O₈
• sanidine (monoclinic)^[7] —(K,Na)AlSi₃O₈
• microcline (triclinic)^[8] — KAlSi₃O₈
• anorthoclase (triclinic) — (Na,K)AlSi₃O₈

Sanidine is stable at the highest temperatures, and microcline at the lowest.^[7][6] Perthite is a typical texture in alkali feldspar, due toexsolution of contrasting alkali feldspar compositions during cooling of an intermediate composition. The perthitic textures in the alkali feldspars of many granites can be seen with the naked eye.^[9] Microperthitic textures in crystals are visible using a light microscope, whereas cryptoperthitic textures can only be seen using an electron microscope.

Plagioclase Feldspars

Labradorite.

The plagioclase feldspars are triclinic. The plagioclase series follows (with percent anorthite in parentheses):

• albite (0 to 10) — NaAlSi₃O₈
• oligoclase (10 to 30) — (Na,Ca)(Al,Si)AlSi₂O₈
• andesine (30 to 50) — NaAlSi₃O₈ — CaAl₂Si₂O₈
• labradorite (50 to 70) — (Ca,Na)Al(Al,Si)Si₂O₈
• bytownite (70 to 90) — (NaSi,CaAl)AlSi₂O₈
• anorthite (90 to 100) — CaAl₂Si₂O₈

Intermediate compositions of plagioclase feldspar also may exsolve to two feldspars of contrasting composition during cooling, but diffusion is much slower than in alkali feldspar, and the resulting two-feldspar intergrowths typically are too fine-grained to be visible with optical microscopes. The immiscibility gaps in the plagioclase solid solution are complex compared to the gap in the alkali feldspars. The play of colors visible in some feldspar of labradorite composition is due to very fine-grained exsolution lamellae.

Barium Feldspars

The barium feldspars are monoclinic and comprise the following:

• celsian — BaAlSi₃O₈
• hyalophane — (K,Na,Ba)(Al,Si)₄O₈

Feldspars can form clay minerals through chemical weathering..^[10]

Uses

Feldspar output in 2005. Click the image for the details.

• Feldspar is a common raw material in the production of ceramics and geopolymers.
• Feldspars are used for thermoluminescence dating and optical dating in earth sciences and archaeology
• Feldspar is one of several abrasive ingredients in Bon Ami, a brand of household cleaner in the USA.

In 2005, Italy was the top producer of feldspar with almost one-fifth world share followed by Turkey, China and Thailand, reports theInternational Monetary Fund.

Hematite

Hematite
Hematite (blood ore) from the US state ofMichigan (unknown scale)
General
Category	Oxide mineral
Chemical formula	iron(III) oxide, Fe2O3, α-Fe2O3
Identification
Color	Metallic gray to earthy red tones
Crystal habit	Tabular to thick crystals
Crystal system	Hexagonal (rhombohedral)
Cleavage	None
Fracture	Uneven to sub-conchoidal
Mohs Scalehardness	5.5 – 6.5
Luster	Metallic to splendent
Streak	Bright red to dark red
Specific gravity	4.9 – 5.3
Refractive index	Opaque
Pleochroism	None
References	[1][2]

Hematite in SEM, magnification 100x

Close-up of hematitic Banded Iron Formation specimen from Upper Michigan. Scale bar is 5.0 mm.

Hematite, also spelled as hæmatite, is the mineral form of Iron(III) oxide (Fe₂O₃), one of several iron oxides. Hematite crystallizes in the rhombohedral system, and it has the samecrystal structure as ilmenite and corundum. Hematite and ilmenite form a completesolid solution at temperatures above 950°C.

Hematite is a mineral, colored black to steel or silver-gray, brown to reddish brown, or red. It ismined as the main ore of iron. Varieties include kidney ore, martite (pseudomorphs aftermagnetite), iron rose and specularite (specular hematite). While the forms of hematite vary, they all have a rust-red streak. Hematite is harder than pure iron, but much more brittle.Maghemite is a hematite- and magnetite-related oxide mineral.

Huge deposits of hematite are found in banded iron formations. Grey hematite is typically found in places where there has been standing water or mineral hot springs, such as those inYellowstone National Park in the United States. The mineral can precipitateout of water and collect in layers at the bottom of a lake, spring, or other standing water.. Hematite can also occur without water, however, usually as the result of volcanic activity.

Clay-sized hematite crystals can also occur as a secondary mineral formed by weatheringprocesses in soil, and along with other iron oxides or oxyhydroxides such as goethite, is responsible for the red color of many tropical, ancient, or otherwise highly weathered soils.

Good specimens of hematite come from England, Mexico, Brazil, Australia, United States andCanada.

Etymology and history

Ancient Egyptian cylindrical seal (left) made from hematite with corresponding impression (right), approximately 14th century BC

The name hematite is derived from the Greek word for blood (haima ἁιμα) because hematite can be red, as in rouge, a powdered form of hematite. The color of hematite lends it well in use as a pigment.

Ochre is a clay that is colored by varying amounts of hematite, varying between 20% and 70%^[3]. Red ochre contains unhydrated hematite, whereas yellow ochre contains hydratedhematite (Fe₂O₃ • H₂O).. The principal use of ochre is for tinting with a permanent color^[3].

The red chalk winning of this mineral was one of the earliest in history of mankind. The powdery mineral was first used 164,000 years ago by the Pinnacle-Point man obviously for social differentiation^[4]. Hematite residues are also found in old graveyards from 80,000 years ago. Near Rydno in Poland and Lovas in Hungary, palaeolitic red chalk mines have been found that are from 5000 BC, belonging to the Linear Pottery culture at the Upper Rhine.

Rich deposits of hematite have been found on the island of Elba that have been mined till the time of the Etruscans.

Ancient Egyptian booby trap

In 2001, Egyptian government archaeologist Zahi Hawass was the first to enter a previously undisturbed tomb, believed to be that of an ancient regional mayor, in the Bahariya Oasisbelow the town of Bawiti. Upon entering the burial chamber, Hawass discovered abooby trapconsisting of 8 inches of finely powdered hematite dust covering the floor and sarcophagus.^[5]When disturbed by a tomb robber, the sharp, metallic dust was intended to become airborne and irritate the skin, eyes and mucous membranes, eventually causing lethal siderosis if exposed for long enough. The archaeological team was forced to retreat and don full body suits and respirators in order to confirm the identity of the mummy. Hawass cites the ancient Egyptians’ experience with powdered hematite as a paint pigment as proof that they were aware of its irritating properties.^[6]

Jewelry

Hematite carving, 5 cm (2 in) long.

Hematite’s popularity in jewelry was at its highest in Europe during the Victorian era, and has since seen a strong resurgence inNorth America, especially in the western United States.. Due to it delicate nature, the mineral is found only in precious jewelry. Extreme care should be taken in handling hematite items due to the material’s susceptibility to irreversible damage.

It is also used in art such as intaglios where it is used for making hollow portraits.

Magnetism

crystal structure of hematite

Hematite is an antiferromagnetic material below the Morin transition at 250 K, and a canted antiferromagnet or weakly ferromagneticabove the Morin transition and below its Néel temperature at 948K, above which it is paramagnetic.

The magnetic structure of a-hematite was the subject of considerable discussion and debate in the 1950s because it appeared to be ferromagnetic with a Curie temperature of around 1000 K, but with an extremely tiny moment (0.002 µ_B). Adding to the surprise was a transition with a decrease in temperature at around 260 K to a phase with no net magnetic moment. It was shown that the system is essentially antiferromagnetic but that the low symmetry of the cation sites allows spin–orbit coupling to cause canting of the moments when they are in the plane perpendicular to the c axis. The disappearance of the moment with a decrease in temperature at 260 K is caused by a change in the anisotropy which causes the moments to align along the c axis. In this configuration, spin canting does not reduce the energy.^[7][8]

Hematite is part of a complex solid solution oxyhydroxide system having various degrees of water, hydroxyl group, and vacancy substitutions that affect the mineral’s magnetic and crystal chemical properties.^[9] Two other end-members are referred to as protohematite and hydrohematite.

Iron from mine tailings

Hematite is present in the waste tailings of iron mines. A recently developed process,magnetation, uses huge magnets to glean waste hematite from old mine tailings inMinnesota‘s vast Mesabi Range iron district.^[10]

Hematite on Mars

Image mosaic from the Mars Exploration Rover Microscopic Imager shows Hematitespherules partly embedded in rock at the Opportunity landing site. (Scale: image is approximately 5 cm (2 in) across)

The spectral signature of hematite was seen on the planet Mars by the infrared spectrometeron the NASA Mars Global Surveyor(“MGS”) and 2001 Mars Odyssey spacecraft in orbit around Mars.^[11] The mineral was seen in abundance at two sites ^[12] on the planet, the Terra Meridiani site, near the Martian equator at 0° longitude, and the second site Aram Chaos near the Valles Marineris.^[13] Several other sites also showed hematite, e.g., Aureum Chaos.^[14]Because terrestrial hematite is typically a mineral formed in aqueous environments, or by aqueous alteration, this detection was scientifically interesting enough that the second of the two Mars Exploration Rovers was targeted to a site in the Terra Meridiani region designatedMeridiani Planum. In-situ investigations by the Opportunity rover showed a significant amount of hematite, much of it in the form of small spherules that were informally tagged by the science team “blueberries”. Analysis indicates that these spherules are apparentlyconcretions formed from a water solution.

Nephrite

Nephrite
Nephrite
General
Category	Mineral
Chemical formula	Ca2(Mg,Fe)5Si8O22(OH)2[1]
Identification
Color	Translucent to opaque and often mottled. Light to dark green, yellow to brown, white, gray, black.[1]
Crystal habit	massive[1]
Crystal system	monoclinic[1]
Fracture	splintery to granular[1]
Mohs Scalehardness	6 – 6.5[1]
Luster	dull[1]
Specific gravity	2.95 (+.15, -.05)[1]
Polish luster	vitreous to greasy[1]
Optical properties	Double refractive with anomalous aggregate reaction[1]
Refractive index	1.606 – 1.632 (+.009, -.006)[1]
Birefringence	usually not detectable[1]
Pleochroism	none[1]
Ultravioletfluorescence	inert[1]
Absorption spectra	Vague line may be present at 500 nm, but rarely any lines. Rarely, in stones of exceptional gem quality, vague lines in the red part of the spectrum may be seen.[1]

Nephrite is a variety of the calcium and magnesium-rich amphibole mineral actinolite(aggregates of which also make up one form ofasbestos). The chemical formula for nephrite isCa₂(Mg,Fe)₅Si₈O₂₂(OH)₂.^[1] It is one of two different mineral species called jade. The other mineral species known as jade is jadeite, which is a variety of pyroxene. While nephrite jade possess mainly grays and greens (and occasionally yellows, browns or whites), Jadeite jade, which is rarer, can also contain blacks, reds, pinks and violets. Nephrite jade is an ornamental stone, used in carvings, beads, or cabochon cut gemstones.

The name nephrite is derived from lapis nephriticus, which means ‘kidney stone’ and is the Latin version of the Spanish piedra de ijada.^[2] Accordingly, nephrite jade was once believed to be a cure for kidney stones.

Nephrite can be found in a translucent white to very light yellow form which is known in China as mutton fat jade,^[1] in an opaque white to very light brown or gray which is known aschicken bone jade,^[1] as well as in a variety of green colours. Canada is the principal source of modern lapidary nephrite. Nephrite jade was used mostly in pre-1800 China as well as in New Zealand, the Pacific Coast and Atlantic Coasts of North America, Neolithic Europe, and southeast Asia.

History

Prehistoric and historic China

During Neolithic times, the key known sources of nephrite jade in China for utilitarian and ceremonial jade items were the now depleted deposits in the Ningshao area in the Yangtze River Delta (Liangzhu culture 3400–2250 BC) and in an area of the Liaoning province in Inner Mongolia (Hongshan culture 4700–2200 BC). Jade was used to create many utilitarian and ceremonial objects, ranging from indoor decorative items to jade burial suits. Jade was considered the “imperial gem”. From about the earliest Chinese dynasties until present, the jade deposits in most use were from the region of Khotan in the Western Chinese province ofXinjiang(jade deposits from other areas of China, such as Lantian, Shaanxi, were also in great demand). There, white and greenish nephrite jade is found in small quarries and as pebbles and boulders in the rivers flowing from the Kuen-Lun mountain range northward into theTakla-Makan desert area. River jade collection was concentrated in the Yarkand, the White Jade (Yurungkash) and Black Jade (Karakash) Rivers. From the Kingdom of Khotan, on the southern leg of the Silk Road, yearly tribute payments consisting of the most precious white jade were made to the Chinese imperial court and there transformed into objets d’art by skilled artisans, as jade was considered more valuable than gold or silver.

Māori

Nephrite jade in New Zealand is known as pounamu in the Māori language, and is highly valued, playing an important role in Māoriculture. It is considered a taonga, or treasure, and therefore protected under the Treaty of Waitangi, and the exploitation of it is restricted and closely monitored. The South Island of New Zealand is Te Wai Pounamu in Māori — “The [land of] Greenstone Water” — because that is where it occurs.

Nephrite

Weapons and ornaments were made of it; in particular the mere (short club), and the hei-tiki(neck pendant). These were believed to have their own mana, were handed down as valuable heirlooms, and often given as gifts to seal important agreements. It was also used for a range of tools such as adzes, as Māori had no metal tools.

In New Zealand English its normal name is “greenstone”. Jade jewellery in Māori designs is widely popular with locals of all races, and with tourists – although much of the jade itself is now imported from British Columbia and elsewhere.

Other names

Besides the terms already mentioned, nephrite has the following synonyms and varieties:aotea, axe-stone, B.C. jade, beilstein,kidney stone, lapis nephriticus, nephrit, nephrita, New Zealand greenstone,^[1] New Zealand jade,^[1] spinach jade (dark grayish green),^[1] and talcum nephriticus. Tomb jade or grave jade are names given to ancient burial nephrite pieces that have a brown or chalky white texture as a surface treatment.^[1]

Jade

A selection of antique, hand craftedChinesejade (jadeite) buttons.

Unworked jade

Jade is an ornamental stone. The term jade is applied to two different metamorphic rocks that are made up of different silicate minerals:

• Nephrite jade, consists of a microcrystaline interlocking fibrous matrix of the calcium, magnesium-iron rich amphibole mineral series tremolite (calcium-magnesium)-ferroactinolite (calcium-magnesium-iron). The middle member of this series with an intermediate composition is calledactinolite (the silky fibrous mineral form is one form of asbestos). The higher the iron content the greener the colour.
• Jadeitite, a rock consisting almost entirely of jadeite, a sodium- and aluminium-rich pyroxene. The gem form of the mineral is a microcrystaline interlocking crystal matrix.

The English word jade is derived from the Spanish term piedra de ijada (first recorded in 1565) or “loin stone”, from its reputed efficacy in curing ailments of the loins and kidneys. Nephrite is derived from lapis nephriticus, the Latin version of the Spanish piedra de ijada.^[1]

Nephrite and jadeite were used by people from the prehistoric for similar purposes. Jadeite has about the same hardness as quartz, while nephrite is somewhat softer. Both nephrite and jadeite are tough, but nephrite is tougher than jadeite. They can be delicately shaped. Thus it was not until the 19th century that a French mineralogist determined that “jade” was in fact two different materials. The trade name jadite is sometimes applied to translucent or opaque green glass.

Among the earliest known jade artifacts excavated from prehistoric sites are simple ornaments with bead, button, and tubular shapes.^[2] Additionally, jade was used for axe heads, knives, and other weapons. As metal-working technologies became available, the beauty of jade made it valuable for ornaments and decorative objects. Jadeite measures between 6.5 and 7.0 Mohs hardness, and Nephrite between 5.5 and 6.0,^[3] so it can be worked with quartz or garnet sand, and polished with bamboo or even ground jade.

Nephrite can be found in a creamy white form (known in China as “mutton fat” jade) as well as in a variety of green colours, whereas jadeite shows more colour variations, including blue, lavender-mauve, pink, and emerald-green colours. Of the two, jadeite is rarer, documented in fewer than 12 places worldwide. Translucent emerald-green jadeite is the most prized variety, both today and historically. As “quetzal” jade, bright green jadeitite from Guatemala was treasured by Mesoamerican cultures, and as “kingfisher” jade, vivid green rocks from Burma became the preferred stone of post-1800 Chinese imperial scholars and rulers. Burma (Myanmar) and Guatemala are the principal sources of modern gem jadeitite, and Canada of modern lapidary nephrite. Nephrite jade was used mostly in pre-1800 China as well as in New Zealand, the Pacific Coast and Atlantic Coasts of North America, Neolithic Europe, and south-east Asia.. In addition to Mesoamerica, jadeite was used by Neolithic Japanese and European cultures.

Jade is the official gemstone of British Columbia, where it is found in large deposits in the Lillooet andCassiar regions. It is also the official gemstone of the state of Alaska, found particularly in the Kobuk area. A two-ton block of jade sits outside the Anchorage Visitor’s Center in downtown Anchorage, Alaska, mined from near Kobuk and donated to the city as a showpiece. Jade is also the state gemstone of the State ofWyoming.^{[citations needed]}

The 2008 Summer Olympic medals have a ring of jade in them.

History

Prehistoric and Historic China

Jade dragon, Western Han Dynasty (202 BC-9 AD)

During Neolithic times, the key known sources of nephrite jade in China for utilitarian and ceremonial jade items were the now depleted deposits in the Ningshao area in the Yangtze River Delta (Liangzhu culture3400–2250 BC) and in an area of the Liaoning province and Inner Mongolia (Hongshan culture 4700–2200 BC).^[4] As early as 6000 BC Dushan Jade has been mined.. In the Yin Ruins of Shang Dynasty (1600 BC to 1050 BC) in Anyang, Dushan Jade ornaments was unearthed in the tomb of the Shang kings. Jade was used to create many utilitarian and ceremonial objects, ranging from indoor decorative items to jade burial suits. Jade was considered the “imperial gem”. From about the earliest Chinese dynasties until present, the jade deposits in most use were not only from the region of Khotan in the Western Chinese province ofXinjiang but also from other parts of China, such as Lantian, Shaanxi. There, white and greenish nephrite jade is found in small quarries and as pebbles and boulders in the rivers flowing from the Kuen-Lun mountain range northward into the Takla-Makan desert area. River jade collection was concentrated in theYarkand, the White Jade (Yurungkash) and Black Jade (Karakash) Rivers. From the Kingdom of Khotan, on the southern leg of the Silk Road, yearly tribute payments consisting of the most precious white jade were made to the Chinese Imperial court and there transformed intoobjets d’art by skilled artisans as jade was considered more valuable than gold or silver. Jade became a favorite material for the crafting of Chinese scholars objects, such as rests for calligraphy brushes, as well as the mouthpieces of some opium pipes, due to the belief that breathing through jade would bestow longevity upon smokers who used such a pipe.^[5]

Jadeite, with its bright emerald-green, pink, lavender, orange and brown colours was imported from Burmato China only after about 1800. The vivid green variety became known as Feicui (翡翠) or Kingfisher (feathers) Jade. It quickly replaced nephrite as the imperial variety of jade.

In the long history of the art and culture of the enormous Chinese empire, jade has always had a very special significance, roughly comparable with that of gold and diamonds in the West. Jade was used not only for the finest objects and cult figures, but also in grave furnishings for high-ranking members of the imperial family.

Prehistoric and Early Historic Korea

Korean National Treasure No. 191, a gold crown with comma-shaped jades, was excavated from theHeavenly Horse Tomb of Sillaand dates to the 5th century AD.

The use of jade and other greenstone was a long-term tradition in Korea (c. 850 BC – AD 668). Jade is found in small numbers of pit-houses and burials. The craft production of small comma-shaped and tubular ‘jades’ using materials such as jade, microcline, jasper, etc in southern Korea originates from the MiddleMumun Pottery Period (c. 850–550 BC).^[6] Comma-shaped jades are found on some of the gold crowns ofSilla royalty (c. AD 300/400–668) and sumptuous elite burials of the Korean Three Kingdoms. After the state of Silla united the Korean Peninsula in AD 668, the widespread popularisation of death rituals related to Buddhism resulted in the decline of the use of jade in burials as prestige mortuary goods.

Māori

Nephrite jade in New Zealand is known as pounamu in the Māori language, playing an important role inMāori culture. It is considered a taonga, or treasure, and therefore protected under the Treaty of Waitangi, and the exploitation of it is restricted and closely monitored. It is found only in the South Island of New Zealand, known as Te Wai Pounamu in Māori — “The [land of] Greenstone Water”, or Te Wahi Pounamu— “The Place of Greenstone”.

Tools, weapons and ornaments were made of it; in particular adzes, the ‘mere‘ (short club), and the Hei-tiki(neck pendant). These were believed to have their own mana, handed down as valuable heirlooms, and often given as gifts to seal important agreements.

One name used for nephrite jade in New Zealand English is “greenstone.” While widely used to describe the material used for jewellery items made for the tourist trade, it is a misnomer and simply engenders confusion. The stone should be correctly referred to as “nephrite” or “nephrite jade”. Nephrite jewellery of Maori design is widely popular with locals and tourists, although some of the jade used for these is now imported from British Columbia and elsewhere.^[7]

Mesoamerica

Jadeite Pectoral from theMayan Classic period. (195 mm/7.7 in high)

Jade pendant, found in a tomb in Tikal, Guatemala

Jade was a rare and valued material in pre-Columbian Mesoamerica. The only source from which the various indigenous cultures, such as theOlmec and Maya, for example, could obtain jade was located in theMotagua River valley in Guatemala. Jade was largely an elite good, and was usually carved in a variety ways, whether serving as a medium upon which hieroglyphs were inscribed, or shaped into symbolic figurines.. Generally, the material was highly symbolic, and it was often employed in the performance of ideological practices and rituals.

Today, Guatemala produces jadeite in a variety of colours, ranging from soft translucent lilac, blue, green, yellow, and black. It is also the source of new colours, including “rainbow jade” and the unique “Galactic Gold,” a black jadeite with natural incrustations of gold, silver and platinum.^[8]

Prehistoric and Historic India

The Jainist temple of Kolanpak in the Nalgonda district, Andhra Pradesh,India is home to a 5-foot (1.5 m) high sculpture of Mahavira that is carved entirely out of jade. The is the largest sculpture made from a single jade rock in the world.

Other names

Besides the terms already mentioned, jadeite and nephrite are sometimes referred to by the following:

Jadeite

• Agate verdâtre
• Feitsui
• Jadeit
• Jadeita
• Natronjadeit
• Yunnan Jade
• Yu-stone

Nephrite

• Aotea
• Axe-stone
• B.C. Jade
• Beilstein
• British Columbian Jade
• Canadian Jade
• Dushan Jade
• Nanyang Jade
• Du Jade
• Henan Yu
• Grave Jade
• Kidney Stone
• Lapis Nephriticus
• Nephrit
• Nephrita
• Nephrite (of Werner)
• New Zealand Greenstone
• New Zealand Jade
• Siberian Jade
• Sinkiang jade
• Spinach Jade
• Talcum Nephriticus
• Tomb Jade

Faux jade

Many minerals are sold as jade. Some of these are: serpentine (also bowenite), carnelian, aventurine quartz, glass, grossularite,Vesuvianite, soapstone (and other steatites such as shoushan stone) and recently, Australian chrysoprase. “Korean jade,” “Suzhou jade,” “Styrian jade,” “Olive jade”, and “New jade” are all really serpentine; “Transvaal jade” or “African jade” is grossularite; “Peace jade” is a mixture of serpentine, stichtite, and quartz; “Mountain jade” is dyed dolomite marble.

In almost all dictionaries, the Chinese character ‘yù’ (玉) is translated into English as ‘jade’. However, this frequently leads to misunderstanding: Chinese, Koreans, and Westerners alike generally fail to appreciate that the cultural concept of ‘jade’ is considerably broader in China and Korea than in the West. A more accurate translation for this character on its own would be ‘precious/ornamental rock’. It is seldom, if ever, used on its own to denote ‘true’ jade in Mandarin Chinese; for example, one would normally refer to ‘ying yu’ (硬玉, ‘hard jade’) for jadeite, or ‘ruan yu’ (軟玉, ‘soft jade’) for nephrite. The Chinese names for many ornamental non-jade rocks also incorporate the character ‘yù’, and it is widely understood by native speakers that such stones are not, in fact, true precious nephrite or jadeite. Even so, for commercial reasons, the names of such stones may well still be translated into English as ‘jade’, and this practice continues to confuse the unwary.

Enhancement

Jade may be enhanced (sometimes called “stabilized”). There are three main methods, sometimes referred to as the ABC Treatment System:

• Type A jadeite has not been treated in any way except surface waxing.
• Type B treatment involves exposing a promising but stained piece of jadeite to chemical bleaches and/or acids and impregnating it with a clear polymer resin. This results in a significant improvement of transparency and colour of the material. Currently, infrared spectroscopy is the most accurate test for the detection of polymer in jadeite.
• Type C jade has been artificially stained or dyed. The red colour of Red jade can be enhanced with heat. The effects are somewhat uncontrollable and may result in a dull brown. In any case, translucency is usually lost.
• B+C jade is a combination of B and C: it has been both artificially dyed AND impregnated.
• Type D jade refers to a composite stone such as a doublet comprising a jade top with a plastic backing.^[9]

Gallery of Chinese jades

Jade dragon ring, Shang Dynasty (1700 BC-1150 BC)	Jade dragon, Warring States (403 BC-221 BC)	A jade Bi with dragons,Warring States(403 BC-221 BC)	Jade coiled serpent, Han Dynasty (202 BC-220 AD)
Jade-dragon belt clasp, Liu Song Dynasty(420-479AD)	Jade dragon, Tang Dynasty (618-907 AD)	Belt plaque with dragon,Yuan Dynasty(1279-1368AD)	Belt plaque with dragon,Ming Dynasty(1368-1644AD)

Agate

Agate
Moss agate pebble, 2.5 cm (1 inch) long
General
Category	Quartz variety
Chemical formula	Silica, SiO2
Identification
Color	White to grey, light blue, orange to red, black.
Crystal habit	Cryptocrystalline silica
Crystal system	Rhombohedral Microcrystalline
Cleavage	None
Fracture	Conchoidal with very sharp edges.
Mohs Scalehardness	7
Luster	Waxy
Streak	White
Specific gravity	2.58-2.64
Refractive index	1.530-1.540
Birefringence	up to +0.004 (B-G)
Pleochroism	Absent

Agate (pronounced /ˈæɡət/) is a microcrystalline variety of quartz (silica), chiefly chalcedony, characterised by its fineness of grain and brightness of color. Although agates may be found in various kinds of rock, they are classically associated with volcanic rocks but can be common in certainmetamorphic rocks.^[1]

Colorful agates and other chalcedonies were obtained over 3,000 years ago from the Achates River, now called Dirillo, in Sicily.^[2]

The stone was given its name by Theophrastus, a Greek philosopher and naturalist, who discovered the stone along the shore line of the river Achates (Greek: Αχάτης) sometime between the 4th and 3rd centuries BC.^[3] The agate has been recovered at a number of ancient sites, indicating its widespread use in the ancient world; for example, archaeological recovery at the Knossos site on Creteillustrates its role in Bronze Age Minoanculture.^[4]

Formation and characteristics

Most agates occur as nodules in volcanic rocks or ancient lavas where they represent cavities originally produced by the disengagement of volatilesin the molten mass which were then filled, wholly or partially, by siliceous matter deposited in regular layers upon the walls. Such agates, when cut transversely, exhibit a succession of parallel lines, often of extreme tenuity, giving a banded appearance to the section. Such stones are known as banded agate, riband agate and striped agate.

In the formation of an ordinary agate, it is probable that waters containing silica in solution—derived, perhaps, from the decomposition of some of the silicates in the lava itself—percolated through the rock and deposited a siliceous coating on the interior of the vapour-vesicles. Variations in the character of the solution or in the conditions of deposition may cause a corresponding variation in the successive layers, so that bands of chalcedony often alternate with layers of crystalline quartz. Several vapour-vesicles may unite while the rock is still viscous, and thus form a large cavity which may become the home of an agate of exceptional size; thus a Brazilian geode lined with amethyst and weighing 67 tons was exhibited at theDusseldorf Exhibition of 1902. Perhaps the most comprehensive review of agate chemistry is a recent text by Moxon cited below.

The first deposit on the wall of a cavity, forming the “skin” of the agate, is generally a dark greenish mineral substance, likeceladonite, delessite or “green earth“, which are rich in iron probably derived from the decomposition of the augite in the enclosing volcanic rock. This green silicate may give rise by alteration to a brown iron oxide (limonite), producing a rusty appearance on the outside of the agate-nodule. The outer surface of an agate, freed from its matrix, is often pitted and rough, apparently in consequence of the removal of the original coating. The first layer spread over the wall of the cavity has been called the “priming”, and upon this base zeolitic minerals may be deposited.

Many agates are hollow, since deposition has not proceeded far enough to fill the cavity, and in such cases the last deposit commonly consists of quartz, often amethyst, having the apices of the crystals directed towards the free space so as to form a crystal-lined cavity, or geode.

On the disintegration of the matrix in which the agates are embedded, they are set free. The agates are extremely resistant to weathering and remain as nodules in the soil or are deposited as gravel in streams and shorelines.

Types of agate

Banded agate (agate-like onyx). The specimen is 2.5 cm (1 inch) wide.	Agatized Coral	Montana moss agate	“Turritella agate” (Elimia tenera) from Green River Formation, Wyoming
Faceted Botswana agate

A Mexican agate, showing only a single eye, has received the name of cyclops agate. Included matter of a green, golden, red, black or other color or combinations embedded in the chalcedony and disposed in filaments and other forms suggestive of vegetable growth, gives rise to dendritic or moss agate. Dendritic agates have fern like patterns in them formed due to the presence of manganese and iron oxides. Other types of included matter deposited during agate-building include sagenitic growths (radial mineral crystals) and chunks of entrapped detritus (such as sand, ash, or mud). Occasionally agate fills a void left by decomposed vegetative material such as a tree limb or root and is called limb cast agate due to its appearance.

Turritella agate is formed from silicified fossil Turritella shells. Turritella are spiral marine gastropods having elongated, spiral shells composed of many whorls. Similarly, coral, petrified wood and other organic remains or porous rocks can also become agatized. Agatized coral is often referred to as Petoskey stone or agate.

Greek agate is a name given to pale white to tan colored agate found in Sicily back to 400 B.C. The Greeks used it for making jewelry and beads. Today any agate of this color from Sicily, once an ancient Greek colony, is called Greek agate. Yet the stone had been around centuries before that and was known to both the Sumerians and the Egyptians, who used the gem for decoration and religious ceremony.

Another type of agate is Brazilian agate, which is found as sizable geodes of layered nodules. These occur in brownish tones interlayered with white and gray. Quartz forms within these nodules, creating a striking specimen when cut opposite the layered growth axis. It is often dyed in various colors for ornamental purposes.

Certain stones, when examined in thin sections by transmitted light, show a diffraction spectrum due to the extreme delicacy of the successive bands, whence they are termed rainbow agates. Often agate coexists with layers or masses of opal, jasper or crystalline quartz due to ambient variations during the formation process.

Other forms of agate include carnelian agate (usually exhibiting reddish hues), Botswana agate, Ellensburg blue agate, blue lace agate, plume agates, tube agate (with visible flow channels), fortification agate (which exhibit little or no layered structure), fire agate (which seems to glow internally like an opal) and Mexican crazy-lace agate (which exhibits an often brightly colored, complex banded pattern) also called Rodeo Agate and Rosetta Stone depending on who owned the mine at the time.

Uses in industry and art

Industry uses agates chiefly to make ornaments such as pins, brooches, paper knives, inkstands, marbles and seals. Because of its hardness and ability to resist acids, agate is used to make mortars and pestles to crush and mix chemicals. Because of the high polish possible with agate it has been used for centuries for leather burnishing tools. Idar-Oberstein was one of the centers which made use of agate on an industrial scale. Where in the beginning locally found agates were used to make all types of objects for the European market, this became a globalized business around the turn of the 20th century: Idar-Oberstein imported large quantities of agate from Brazil, as ship’s ballast. Making using of a variety of proprietary chemical processes, they produced colored beads that were sold around the globe.^[5] Agates have long been used in arts and crafts. The sanctuary of a Presbyterian church in Yachats, Oregon, has six windows with panes made of agates collected from the local beaches.

Chrysoprase

Chrysoprase

Chrysoprase or chrysophrase is a gemstone variety of chalcedony (a cryptocrystalline form of silica) that contains small quantities of nickel. Its color is normally apple-green, but varies to deep green. The darker varieties of chrysoprase are also referred to asprase. (However, the term prase is also used to describe chlorite-included quartz, and to a certain extent is a color-descriptor, rather than a rigorously defined mineral variety.)

Chrysoprase is cryptocrystalline, which means that it is composed of crystals so fine that they cannot be seen as distinct particles under normal magnification. This sets it apart from rock crystal, amethyst, citrine, and the other varieties of crystalline quartz which are basically transparent and formed from easily recognized six-sided crystals. Other members of the cryptocrystalline silica family include agate, carnelian, and onyx. Unlike many non-transparent silica minerals, it is the color of chrysoprase, rather than any pattern of markings, that makes it desirable. The word chrysoprase comes from the Greek chrysos meaning ‘gold’ and prason, meaning ‘leek’.

Unlike emerald which owes its green color to the presence of chromium, the color of chrysoprase is due to trace amounts of nickelcompounds in form of very small inclusions. The nickel reportedly occurs as different silicates, like kerolite or pimelite (not NiO mineral, bunsenite, as was reported before). Chrysoprase results from the deep weathering orlateritization of nickeliferousserpentinites or other ultramafic ophiolite rocks. In the Australian deposits, chrysoprase occurs as veins and nodules with browngoethite and other iron oxidesin the magnesite-rich saprolite below an iron and silica cap.

As with all forms of chalcedony, chrysoprase has a hardness of 6 – 7 on the Mohs hardness scale and a conchoidal fracture like flint.

The best known sources of chrysoprase are Queensland, Western Australia, Germany,Poland, Russia, Arizona, California, andBrazil. The chrysoprase and Ni silicate ore deposit in Szklary, Lower Silesia, Poland, was probably the biggest European chrysoprase occurrence and possibly also the biggest in the world.

A very similar mineral to chrysoprase is chrome chalcedony, in which the color is provided bychromium rather than nickel.

Spodumene

“Kunzite” redirects here. For the Sailor Moon character, see Shitennou.

Spodumene
An almost colorless kunzite crystal (upper left), a cut pale pink kunzite (upper right) and a greenish hiddenite crystal (below) (unknown scale)
General
Category	Mineral
Chemical formula	lithium aluminium silicate, LiAl(SiO3)2
Identification
Color	Highly variable: white, colorless, gray, pink, lilac, violet, yellow and green
Crystal habit	prismatic, generally flattened and elongated
Crystal system	monoclinic; 2/m
Cleavage	Perfect prismatic, two directions at nearly 90°
Fracture	Sub-conchoidal
Mohs Scalehardness	6.5 – 7
Luster	Vitreous
Streak	white
Specific gravity	3.17-3.19
Refractive index	1.66-1.68
Pleochroism	Strong in kunzite: pink, colorless; hiddenite: yellow-green, blue-green
Fusibility	3.5
Solubility	insoluble
Other characteristics	Tenebrescence, chatoyancy, kunzite often fluorescentunderUV

Spodumene is a pyroxene mineral consisting of lithium aluminium inosilicate - LiAl(SiO₃)₂ – and is a source of lithium. It occurs as colorless to yellowish, purplish or lilac kunzite (see below), yellowish-green or emerald-green hiddenite, prismatic crystals, often of great size. Single crystals of 14.3 m in size are reported from the Black Hills of South Dakota, United States.^[1]

Crystals form in the monoclinic system and are typically heavily striated parallel to the principal axis. Crystal faces are often etched and pitted with triangular markings.

Spodumene is derived from the Greek spodumenos (σποδυμενος), meaning “burnt to ashes,” owing to the opaque, ash-grey appearance of material refined for use in industry.

Spodumene occurs in lithium rich granites and pegmatites. Transparent material has long been used as a gemstone with varieties kunzite and hiddenite noted for their strongpleochroism. Source localities include Afghanistan, Australia, Brazil, Madagascar,Pakistanand USA (North Carolina, California).

Economic importance

Spodumene is an important source of lithium for use in ceramics, mobile phone andautomotive batteries, medicine and as a fluxing agent. Lithium is extracted from spodumene by fusing in acid.

World production of lithium via spodumene is around 80,000 metric tonnes per annum, primarily from the Greenbushes pegmatite ofWestern Australia, and some Chinese andChilean sources. The Talison mine in Greenbushes, Western Australia has an estimated reserve of 13 million tonnes.^[2]

Spodumene is becoming less important a source of lithium due to the emergence of alkalinebrine lake sources in Chile, China andArgentina, which produce lithium chloride directly. Lithium chloride is converted to lithium carbonate and lithium hydroxide by reaction withsodium carbonate and calcium hydroxide respectively.

Kunzite

Kunzite
See the pleochroism and the typical etched marks (unknown scale)

Kunzite is a pink to lilac colored gemstone, a variety of spodumene with the color coming from minor to trace amounts ofmanganese. Some (but not all) kunzite used for gemstones has been heated to enhance its color. It is also frequently irradiated to enhance the color. Many kunzites fade when exposed to sunlight. It was discovered in 1902, and was named after George Frederick Kunz, Tiffany & Co‘s chief jeweler at the time, and a noted mineralogist. It has been found in Brazil, USA, Canada, CIS, Mexico,Sweden, Western Australia, Afghanistan and Pakistan.

Tourmaline

Tourmaline
Schorl Tourmaline
General
Category	Silicate mineral group
Chemical formula	(Ca,K,Na,[])(Al,Fe,Li,Mg,Mn)3(Al,Cr, Fe,V)6 (BO3)3(Si,Al,B)6O18(OH,F)4 [1][2]
Identification
Color	Most commonly black, but can range from brown, violet, green, pink, or in a dual-colored pink and green.
Crystal habit	Parallel and elongated. Acicular prisms, sometimes radiating. Massive. Scattered grains (in granite).
Crystal system	Trigonal
Cleavage	Indistinct
Fracture	Uneven, small conchoidal, brittle
Mohs Scalehardness	7–7.5
Luster	Vitreous, sometimes resinous
Streak	White
Specific gravity	3.06 (+.20 -.06)[1]
Density	2.82–3.32
Polish luster	Vitreous[1]
Optical properties	Double refractive, uniaxial negative[1]
Refractive index	nω=1.635–1.675, nε=1.610–1.650
Birefringence	-0.018 to -0.040; typically about .020 but in dark stones it may reach .040[1]
Pleochroism	typically moderate to strong[1] Red Tourmaline: Definite; dark red,light red Green Tourmaline: Strong; dark green, yellow-green Brown Tourmaline: Definite; dark brown, light brown Blue Tourmaline: Strong; dark blue, light blue
Dispersion	.017[1]
Ultravioletfluorescence	pink stones—inert to very weak red to violet in long and short wave[1]
Absorption spectra	a strong narrow band at 498nm, and almost complete absorption of red down to 640nm in blue and green stones; red and pink stones show lines at 458 and 451nm as well as a broad band in the green spectrum[1]

Tourmaline is a crystal silicate mineral compounded with elements such as aluminium, iron,magnesium, sodium, lithium, orpotassium. Tourmaline is classed as a semi-precious stone and the gem comes in a wide variety of colors. The name comes from the Sinhalese word “turamali” or “toramalli”, which applied to different gemstones found in Ceylon (now Sri Lanka).

History

Brightly colored Sri Lankan gem tourmalines were brought to Europe in great quantities by theDutch East India Company to satisfy a demand for curiosities and gems. At the time it was not realised that schorl and tourmaline were the same mineral.

Tourmaline species and varieties

• Dravite species: from the Drave district of Carinthia
  • Dark yellow to brownish black—dravite
• Schorl Species:
  • Bluish or brownish black to Black—schorl
• Elbaite Species: named after the island of Elba, Italy
  • Rose or pink—rubellite variety(from ruby)
  • Dark black—schorl(from indigo)
  • Light blue to bluish green—Brazilian indicolite variety
  • Green—verdelite or Brazilian emerald variety
  • Colorless—achroite variety (from the Greek for “colorless”)