Anandite

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]

Anandite
General
Category	Phyllosilicate minerals, brittle mica group
Formula	(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]

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 first director of the Mineral Survey of Ceylon, Sri Lanka.^[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]