Chamosite

Formula:  (Fe,Mg)5Al(Si3Al)O10(OH,O)8

Origin of name:  Locality; Chamoson, Switzerland

 

Crystal system:  Monoclinic

Crystal class:  2/m

Twinning:

Unit cell: a = 5.373, b = 9.306, c = 14.222, β = 97.88

 

Colour:  Green, greenish grey to black

Diaphaneity: Translucent to subtranslucent

Luster:  Pearly

Habit:  Massive; compact or oolitic

Hardness:  ~ 3

Specific gravity:  3.12

Cleavage:  None

Tenacity: Uneven fracture

Streak:  Green to grey

 

Synonyms/varieties: Brunsvigite, Daphnite, Delessite, Thuringite (Fe)
 

 

Comments:  Dimorphous with orthochamosite; series with clinochlore

 

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