Anandite | |
---|---|
General | |
Category | Phyllosilicates |
Formula (repeating unit) | (Ba,K)(Fe2+,Mg)3(Si,Al,Fe)4O10(S,OH)2 |
IMA symbol | Ana [1] |
Strunz classification | 9.EC.35 |
Crystal system | Monoclinic |
Crystal class | Prismatic (2/m) (same H-M symbol) |
Space group | C2/m |
Unit cell | a = 5.412(5), b = 9.434(5) c = 19.953(10) [Å]; β = 95°; Z = 2 |
Identification | |
Color | Black |
Crystal habit | Massive, prismatic crystals poorly formed produce hexagonal outline cleavage fragments |
Cleavage | Perfect on {001} |
Fracture | Flexible fragments |
Mohs scale hardness | 3 – 4 |
Luster | Vitreous |
Streak | Grey white |
Diaphaneity | Nearly opaque |
Specific gravity | 3.94 |
Optical properties | Biaxial (+) |
Refractive index | nα = 1.855 nγ = 1.880 |
Pleochroism | Y = green; Z = brown |
References | [2] [3] [4] |
Anandite is a rare phyllosilicate with formula (Ba,K)(Fe2+,Mg)3(Si,Al,Fe)4O10(S,OH)2. It crystallizes in the monoclinic crystal system. It is black in color with a glassy luster and a near perfect cleavage. [3]
It was first described in 1967 [3] for an occurrence in the Wilagedera Prospect of the North Western Province of Sri Lanka in bands of iron ore. [2] [4] It has also been found in Big Creek in Fresno County and in Trumball Peak in Mariposa County, California as well as the Sterling Mine in New Jersey. [2] It was named for Ananda Kentish Coomaraswamy (1877–1947), who was the director of the Mineral Survey of Ceylon, Sri Lanka at that time. [4]
Anandite is a member of the mica group of minerals. [3] Other minerals that anandite is associated with include: magnetite, chalcopyrite, pyrite, pyrrhotite and baryte. [3]
Topaz is a silicate mineral made of aluminum and fluorine with the chemical formula Al2SiO4(F, OH)2. It is used as a gemstone in jewelry and other adornments. Common topaz in its natural state is colorless, though trace element impurities can make it pale blue or golden brown to yellow-orange. Topaz is often treated with heat or radiation to make it a deep blue, reddish-orange, pale green, pink, or purple.
Sillimanite or fibrolite is an aluminosilicate mineral with the chemical formula Al2SiO5. Sillimanite is named after the American chemist Benjamin Silliman (1779–1864). It was first described in 1824 for an occurrence in Chester, Connecticut.
Cordierite (mineralogy) or iolite (gemology) is a magnesium iron aluminium cyclosilicate. Iron is almost always present, and a solid solution exists between Mg-rich cordierite and Fe-rich sekaninaite with a series formula: (Mg,Fe)2Al3(Si5AlO18) to (Fe,Mg)2Al3(Si5AlO18). A high-temperature polymorph exists, indialite, which is isostructural with beryl and has a random distribution of Al in the (Si,Al)6O18 rings. Cordierite is also synthesized and used in high temperature applications such as catalytic converters and pizza stones.
Phenakite or phenacite is a fairly rare nesosilicate mineral consisting of beryllium orthosilicate, Be2SiO4. Occasionally used as a gemstone, phenakite occurs as isolated crystals, which are rhombohedral with parallel-faced hemihedrism, and are either lenticular or prismatic in habit: the lenticular habit is determined by the development of faces of several obtuse rhombohedra and the absence of prism faces. There is no cleavage, and the fracture is conchoidal. The Mohs hardness is high, being 7.5–8; the specific gravity is 2.96. The crystals are sometimes perfectly colorless and transparent, but more often they are greyish or yellowish and only translucent; occasionally they are pale rose-red. In general appearance the mineral is not unlike quartz, for which indeed it has been mistaken. Its name comes from Ancient Greek: φέναξ, romanized: phénax, meaning "deceiver" due to its close visual similarity to quartz, named by Nils Gustaf Nordenskiöld in 1833.
Dumortierite is a fibrous variably colored aluminium boro-silicate mineral, Al7BO3(SiO4)3O3. Dumortierite crystallizes in the orthorhombic system typically forming fibrous aggregates of slender prismatic crystals. The crystals are vitreous and vary in color from brown, blue, and green to more rare violet and pink. Substitution of iron and other tri-valent elements for aluminium result in the color variations. It has a Mohs hardness of 7 and a specific gravity of 3.3 to 3.4. Crystals show pleochroism from red to blue to violet. Dumortierite quartz is blue colored quartz containing abundant dumortierite inclusions.
Thorianite is a rare thorium oxide mineral, ThO2. It was originally described by Ananda Coomaraswamy in 1904 as uraninite, but recognized as a new species by Wyndham R. Dunstan. It was so named by Dunstan on account of its high percentage of thorium; it also contains the oxides of uranium, lanthanum, cerium, praseodymium and neodymium. Helium is present, and the mineral is slightly less radioactive than pitchblende, but is harder to shield due to its high energy gamma rays. It is common in the alluvial gem-gravels of Sri Lanka, where it occurs mostly as water worn, small, heavy, black, cubic crystals. The largest crystals are usually near 1.5 cm. Larger crystals, up to 6 cm (2.4 in), have been reported from Madagascar.
Cerite is a complex silicate mineral group containing cerium, formula (Ce,La,Ca)
9(Mg,Fe3+
)(SiO
4)
6(SiO
3OH)(OH)
3. The cerium and lanthanum content varies with the Ce rich species and the La rich species. Analysis of a sample from the Mountain Pass carbonatite gave 35.05% Ce
2O
3 and 30.04% La
2O
3.
Chlorargyrite is the mineral form of silver chloride (AgCl). Chlorargyrite occurs as a secondary mineral phase in the oxidation of silver mineral deposits. It crystallizes in the isometric–hexoctahedral crystal class. Typically massive to columnar in occurrence it also has been found as colorless to variably yellow cubic crystals. The color changes to brown or purple on exposure to light. It is quite soft with a Mohs hardness of 1 to 2 and dense with a specific gravity of 5.55. It is also known as cerargyrite and, when weathered by desert air, as horn silver. Bromian chlorargyrite is also common. Chlorargyrite is water-insoluble.
Neptunite is a silicate mineral with the formula KNa2Li(Fe2+, Mn2+)2Ti2Si8O24. With increasing manganese it forms a series with mangan-neptunite. Watatsumiite is the variety with vanadium replacing the titanium in the formula.
Ekanite is an uncommon silicate mineral with chemical formula Ca
2ThSi
8O
20 or (Ca,Fe,Pb)
2(Th,U)Si
8O
20. It is a member of the steacyite group. It is among the few gemstones that are naturally radioactive. Most ekanite is mined in Sri Lanka, although deposits also occur in Russia and North America. Clear and well-colored stones are rare as the radioactivity tends to degrade the crystal matrix over time in a process known as metamictization.
Edingtonite is a white, gray, brown, colorless, pink or yellow zeolite mineral. Its chemical formula is BaAl2Si3O10·4H2O. It has varieties with tetragonal, orthorhombic or triclinic crystals.
Akhtenskite is a manganese oxide mineral with the chemical formula of MnO2 (or: ε-Mn4+O2) that was named after the Akhtensk deposit in Russia, where it was first discovered and noted in 1979. It can be found in the Akhtensk brown ironstone deposit, in the southern Ural Mountains, on Mt. Zarod, on the Sikhote-Alin Mountains, and in the Primorskiy Krai, all in Russia.
Imogolite is an aluminium silicate clay mineral with the chemical formula Al2SiO3(OH)4. It occurs in soils formed from volcanic ash and was first described in 1962 for an occurrence in Uemura, Kumamoto prefecture, Kyushu Region, Japan. Its name originates from the Japanese word imogo, which refers to the brownish yellow soil derived from volcanic ash. It occurs together with allophane, quartz, cristobalite, gibbsite, vermiculite and limonite.
Caryopilite (synonymous with ectropite and ektropite) is a brown-colored mineral with formula (Mn2+,Mg)3Si2O5(OH)4. The mineral was discovered in 1889 from a mine in Sweden. It was named for the Greek words for walnut and felt in reference to its appearance.
Serendibite is an extremely rare silicate mineral that was first discovered in 1902 in Sri Lanka by Dunil Palitha Gunasekera and named after Serendib, the old Arabic name for Sri Lanka.
Lucchesiite is a new member of tourmaline-group of minerals. Lucchesiite has the formula CaFe3Al6(Si6O18)(BO3)3(OH)3O. It is the calcium and oxygen-analogue of schorl. It has two co-type localizations, one in Czech Republic and the other in Sri Lanka. As the other members of the tourmaline group, it is trigonal.
Anthoinite (IMA symbol: Atn) is an aluminium tungsten oxide mineral with the chemical formula AlWO3(OH)3. Its type locality is Maniema in the Democratic Republic of the Congo.
Alvanite is a zinc nickel aluminium vanadate mineral with the chemical formula (Zn,Ni)Al4(V5+O3)2(OH)12·2H2O. It was originally discovered in the Karatau Mountains.
Aramayoite is a mineral with the chemical formula Ag3Sb2(Bi,Sb)S6. Its type locality is Sud Chichas, Potosí, Bolivia.
Argentobaumhauerite (IMA symbol: Abha) is a rare mineral with the chemical formula Ag1.5Pb22As33.5S72. Its type locality is the Binn valley in Switzerland.