Howlite

Formula:  Ca2B5SiO9(OH)5

Origin of name:   For H. How, Canadian chemist and mineralogist

 

Crystal system:  Monoclinic

Crystal class:  2/m

Twinning: 

Unit cell: a = 12.78 Ǻ, b = 9.33 Ǻ, c = 8.60 Ǻ, β = 104.8°

 

Colour:  White

Diaphaneity: 

Luster:  Subvitreous

Habit:  Crystals tabular; compact nodular masses; chalk-like; earthy; scaly; porcelaneous

Hardness:  3.5

Specific gravity:  2.45

Cleavage:  None

Tenacity: 

Streak: 

 

Synonyms/varieties:

 

Comments: 

 

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