Kröhnkite

Formula:  NaCu(SO4)2 . 2H2O

Origin of name:  For B. Kröhnke, chemist who did first analysis

 

Crystal system:  Monoclinic

Crystal class:  2/m

Twinning:  On {101}, sometimes heart-shaped

Unit cell: a = 5.80 Ǻ, b = 12.65 Ǻ, c = 5.51 Ǻ, β = 108.4°

 

Colour:  Dark blue to dark sky blue, alters to greenish on exposure

Diaphaneity: 

Luster:  Vitreous to greasy

Habit:  Crystals short prismatic or octahedral and somewhat elongated; massive, granular, columnar or fibrous crusts or aggregates

Hardness:  2.5  to 3

Specific gravity:  2.90

Cleavage:  2; {010} perfect, {-101} imperfect

Tenacity: 

Streak: 

 

Synonyms/varieties:

 

Comments: 

 

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