| 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 ProvinceofSri Lanka in bands of iron ore.[2][4] It has also been found in Big CreekinFresno County and in Trumball PeakinMariposa County, California as well as the Sterling MineinNew 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]
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