Hilgardite

Formula:  Ca2B5O9Cl . H2O

Origin of name:  For E. Hilgard, German-American geologist

 

Crystal system:  Triclinic

Crystal class:  1

Twinning: 

Unit cell: 

 

Colour:  Colourless

Diaphaneity:  Transparent

Luster:  Vitreous

Habit: 

Hardness:  5

Specific gravity:  2.71

Cleavage:  2; {100} and {010} perfect

Tenacity: 

Streak: 

 

Synonyms/varieties:

 

Comments:  Data are for hilgardite-1A; there are also -3A and -4M polytypes

 

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