Anandite

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Anandite
General
CategoryPhyllosilicates
Formula
(repeating unit)
(Ba,K)(Fe2+,Mg)3(Si,Al,Fe)4O10(S,OH)2
Strunz classification9.EC.35
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupC2/m
Unit cella = 5.412(5), b = 9.434(5)
c = 19.953(10) [Å]; β = 95°; Z = 2
Identification
ColorBlack
Crystal habitMassive, prismatic crystals poorly formed produce hexagonal outline cleavage fragments
CleavagePerfect on {001}
FractureFlexible fragments
Mohs scale hardness3 – 4
LusterVitreous
StreakGrey white
DiaphaneityNearly opaque
Specific gravity3.94
Optical propertiesBiaxial (+)
Refractive indexnα = 1.855 nγ = 1.880
PleochroismY = green; Z = brown
References[1][2][3]

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.[2]

It was first described in 1967[2] for an occurrence in the Wilagedera Prospect of the North Western Province of Sri Lanka in bands of iron ore.[1][3] 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.[1] It was named for Ananda Kentish Coomaraswamy (1877–1947), who was the director of the Mineral Survey of Ceylon, Sri Lanka at that time.[3]

Anandite is a member of the mica group of minerals.[2] Other minerals that anandite is associated with include: magnetite, chalcopyrite, pyrite, pyrrhotite and baryte.[2]

References[edit]

  1. ^ a b c "Anandite mineral information and data". Mindat.org.
  2. ^ a b c d e "PDF data sheet for Anandite in the Handbook of Mineralogy" (PDF). Handbook of Mineralogy. Mineral Data Publishing. 2001. Retrieved 2008-05-04.
  3. ^ a b c "Anandite mineral data sheet". Webmineral.com. Archived from the original on 6 May 2008. Retrieved 2008-05-04.