Anandite

Formula:  (Ba,K)(Fe,Mg)₃(Si,Al,Fe)₄O₁₀(S,OH)₂

Origin of name:  For Ananda Kentush Coomaraswamy (1877-1947), of Sri Lanka, first Director of the Mineral Survey of Ceylon (Sri Lanka)

Crystal system:  Monoclinic or Orthorhombic

Crystal class:  2/m or 2/m 2/m 2/m

Twinning:

Unit cell: a = 5.412 Å, b = 9.434 Å, c = 19.878 Å, b = 94°52'

Colour:  Black

Diaphaneity: Nearly opaque

Luster:  Vitreous

Habit:  Massive; cleavage flakes with hexagonal outlines

Hardness:  3 to 4

Specific gravity:  3.94

Cleavage:  1; {001} perfect

Tenacity:

Streak: Gray white

Synonyms/varieties:

Comments:  Data are for anandite-2M₁; there are also  -2O and 1M polytypes. Member of the mica group. Formed as monomineralic veinlets and lenses in a banded magnetite deposit capped by banded magnetite-barite rock. The ore zone and associated interbedded calc-schists and gneisses are of metasedimentary origin, of approximately granulite facies grade.