Formula: HgSe
Origin of name: for Johann Carl Wilhelm Ferdinand Tiemann (1848–1899), chemist of Berlin, Germany, who discovered the mineral.
Crystal system: Isometric/cubic
Crystal class: 43m
Twinning: Common with [111] as twin axis
Unit cell: a = 6.085
Colour: Steel gray to brownish lead-gray, with purplish tint
Diaphaneity: Opaque
Luster: Metallic
Habit: Crystals tetrahedral, {111] typically dull, {111} is brigth, may be striated parallel [110], massive, compact, granular
Hardness: 2.5
Specific gravity: 8.19 to 8.47
Cleavage: None
Tenacity: Brttle, uneven to conchoidal fracture
Streak: Nearly black
Synonyms/varieties:
Comments: polymorphous with cinnabar, hypercinnabar and metacinnabar. Found in hydrothermal veins, usually with other selenides and calcite.
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