Formula: Tl2(Cu,Fe)4S4
Origin of name: from composition, THALlium, CUprum (Copper), and Sulfur
Crystal system: Tetragonal
Crystal class: 42m, 4mm, 422, or 4/m 2/m 2/m
Twinning:
Unit cell: a = 3.882, c = 13.25
Colour: Bronzy-black
Diaphaneity: Opaque
Luster: Metallic
Habit: As bladed crystals, to 1 mm, most commonly as grains
Hardness: 2.5 - 3
Specific gravity: 6.15
Cleavage: 1; parallel to elongation, good
Tenacity: Brittle fracture
Streak:
Synonyms/varieties:
Comments: Found in base-metal sulfide deposits and in high-alkali massifs.
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