Naumannite

Formula: Ag2Se

Origin of name: for Karl Naumann, German crystallographer

 

Crystal system: orthorhombic, pseudocubic

Crystal class: 222

Twinning: 

Unit cell: a = 4.333 Å, b = 7.062 Å, c = 7.764 Å

 

Colour: grayish iron-black, tarnishes to iridescent brownish

Diaphaneity: 

Luster: metallic

Habit: crystals cubic, massive granular, thin plates

Hardness: 2.5

Specific gravity: 7.69 to 7.79

Cleavage: none

Tenacity: hackly, sectile and malleable

Streak: iron-black

 

Synonyms/varieties:

 

Comments: 

 

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