Amesite | |
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General | |
Category | Phyllosilicates Kaolinite-serpentine group |
Formula (repeating unit) | Mg2Al2SiO5(OH)4 |
IMA symbol | Ame [1] |
Strunz classification | 9.ED.15 |
Crystal system | Triclinic |
Crystal class | Pedial (1) (same H-M symbol) |
Space group | C1 |
Unit cell | a = 5.307(1), b = 9.195(2) c = 14.068(3) [Å] α = 90.09(2)° β = 90.25(2)°, γ = 89.96(2)°; Z = 4 |
Identification | |
Color | White, colorless, pink to lilac, pale green |
Crystal habit | Crystals form as platy to tapering elongated pseudohexagonal prisms |
Twinning | Common as six-fold sector twins on {001} and polysynthetic twins parallel to {010} |
Cleavage | Perfect on {001} |
Tenacity | Brittle |
Mohs scale hardness | 2.5-3 |
Luster | Pearly |
Streak | White with pale green tint |
Diaphaneity | Transparent to translucent |
Specific gravity | 2.77 |
Optical properties | Biaxial (+) |
Refractive index | nα = 1.597 nβ = 1.599 nγ = 1.615 |
Birefringence | δ = 0.018 |
Other characteristics | Kaolinite-Serpentine group |
References | [2] [3] [4] |
Amesite is a mineral with general formula of Mg2Al2SiO5(OH)4. [3]
Amesite crystallizes in the triclinic crystal system. [5] It contains three axes of unequal length, not at right angles.
It was first described in 1876 for an occurrence in the Chester Emery Mines, Chester, Hampden County, Massachusetts. It was named for mine owner James Ames. [4] [3] It occurs in an environment of low-grade metamorphism affecting rocks with high aluminium and magnesium content. It occurs associated with vesuvianite, chlorite, magnetite, rutile, diaspore, grossular, calcite, diopside and clinozoisite in various locations. [2]
Amesite is an uncommon silicate mineral which has been reported from a variety of locations worldwide. [3] Amesite has the first reported natural occurrence of the 6R polytype for a trioctahedral 1:1 layer silicate. [6]
Sillimanite 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.
Uvarovite is a chromium-bearing garnet group species with the formula: Ca3Cr2(SiO4)3. It was discovered in 1832 by Germain Henri Hess who named it after Count Sergei Semenovitch Uvarov (1765–1855), a Russian statesman and amateur mineral collector. It is classified in the ugrandite group alongside the other calcium-bearing garnets andradite and grossular.
Tremolite is a member of the amphibole group of silicate minerals with composition: Ca2(Mg5.0-4.5Fe2+0.0-0.5)Si8O22(OH)2. Tremolite forms by metamorphism of sediments rich in dolomite and quartz. Tremolite forms a series with actinolite and ferro-actinolite. Pure magnesium tremolite is creamy white, but the color grades to dark green with increasing iron content. It has a hardness on Mohs scale of 5 to 6. Nephrite, one of the two minerals of the gemstone jade, is a green variety of tremolite.
Oldhamite is a calcium magnesium sulfide mineral with the chemical formula (Ca,Mg)S. Ferrous iron may also be present in the mineral resulting in the chemical formula (Ca,Mg,Fe)S. It is a pale to dark brown accessory mineral in meteorites. It crystallizes in the cubic crystal system, but typically occurs as anhedral grains between other minerals.
Afghanite, (Na,K)22Ca10[Si24Al24O96](SO4)6Cl6, is a hydrous sodium, calcium, potassium, sulfate, chloride, carbonate alumino-silicate mineral. Afghanite is a feldspathoid of the cancrinite group and typically occurs with sodalite group minerals. It forms blue to colorless, typically massive crystals in the trigonal crystal system. The lowering of the symmetry from typical (for cancrinite group) hexagonal one is due to ordering of Si and Al. It has a Mohs hardness of 5.5 to 6 and a specific gravity of 2.55 to 2.65. It has refractive index values of nω=1.523 and nε=1.529. It has one direction of perfect cleavage and exhibits conchoidal fracture. It fluoresces a bright orange.
Afwillite is a calcium hydroxide nesosilicate mineral with formula Ca3(SiO3OH)2·2H2O. It occurs as glassy, colorless to white prismatic monoclinic crystals. Its Mohs scale hardness is between 3 and 4. It occurs as an alteration mineral in contact metamorphism of limestone. It occurs in association with apophyllite, natrolite, thaumasite, merwinite, spurrite, gehlenite, ettringite, portlandite, hillebrandite, foshagite, brucite and calcite.
Fraipontite is a zinc aluminium silicate mineral with a formula of (Zn,Al)3(Si,Al)2O5(OH)4.
Eucryptite is a lithium bearing aluminium silicate mineral with formula LiAlSiO4. It crystallizes in the trigonal - rhombohedral crystal system. It typically occurs as granular to massive in form and may pseudomorphically replace spodumene. It has a brittle to conchoidal fracture and indistinct cleavage. It is transparent to translucent and varies from colorless to white to brown. It has a Mohs hardness of 6.5 and a specific gravity of 2.67. Optically it is uniaxial positive with refractive index values of nω = 1.570 - 1.573 and nε = 1.583 - 1.587.
Carletonite is a rare silicate mineral with formula KNa4Ca4(CO3)4Si8O18(F,OH)·(H2O).
Kegelite is a complex silicate mineral with formula Pb8Al4Si8O20(SO4)2(CO3)4(OH)8.
Iranite (Persian: ایرانیت) is a triclinic lead copper chromate silicate mineral with formula Pb10Cu(CrO4)6(SiO4)2(F,OH)2. It was first described from an occurrence in Iran. It is the copper analogue of hemihedrite (Pb10Zn(CrO4)6(SiO4)2(F,OH)2).
Ashburtonite is a rare lead copper silicate-bicarbonate mineral with formula: HPb4Cu2+4Si4O12(HCO3)4(OH)4Cl.
Stillwellite-(Ce) is a rare-earth boro-silicate mineral with chemical formula (Ce,La,Ca)BSiO5.
Boltwoodite is a hydrated potassium uranyl silicate mineral with formula HK(UO2)(SiO4)·1.5(H2O). It is formed from the oxidation and alteration of primary uranium ores. It takes the form of a crust on some sandstones that bear uranium. These crusts tend to be yellowish with a silky or vitreous luster.
Cymrite is a silicate mineral with the chemical formula BaAl2Si2(O,OH)8·H2O. The mineral is named for Cymru, which is the Welsh word for Wales.
Gilalite is a copper silicate mineral with chemical composition of Cu5Si6O17·7(H2O).
Larnite is a calcium silicate mineral with formula: Ca2SiO4. It is the calcium member of the olivine group of minerals.
Sonolite is a mineral with formula Mn9(SiO4)4(OH,F)2. The mineral was discovered in 1960 in the Sono mine in Kyoto Prefecture, Japan. In 1963, it was identified as a new mineral and named after the Sono mine.
Minnesotaite is an iron silicate mineral with formula: (Fe2+,Mg)3Si4O10(OH)2. It crystallizes in the triclinic crystal system and occurs as fine needles and platelets with other silicates. It is isostructural with the pyrophyllite-talc mineral group.
Hemihedrite is a rare lead zinc chromate silicate mineral with formula Pb10Zn(CrO4)6(SiO4)2(F,OH)2. It forms a series with the copper analogue iranite.