Avicennite

Formula:  Tl2O3

Origin of name:  For Avicennna (930-1037), medieval Arab (Uzbek, Persian) physician and philosopher, who lived in Bukhara, Tadzhikistan

 

Crystal system:  Cubic

Crystal class:  2/m -3

Twinning:

Unit cell: a = 10.547 Å

 

Colour:  Grayish-black

Diaphaneity: Opaque

Luster:  Metallic

Habit:  Small crystals, as coating on carlinite

Hardness:  1.5-2.5

Specific gravity:  8.9

Cleavage:  None

Tenacity: Very brittle

Streak:  Grayish-black, black with brownish tint

 

Synonyms/varieties:

 

Comments: Found in the weathered zone of a hematite-calcite vein cutting banded marmorised and silicified limestones near a granite-gneiss contact; formed by oxidation of carlinite in carbonaceous gold ores in silicified limestones and quartz.

 

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