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Category Sulfide mineral
(repeating unit)
Strunz classification 2.CB.05a
Crystal symmetry Isometric hextetrahedral
H-M symbol: (43m)
Space group: F43m
Unit cell a = 5.8717(5) Å; Z=4
Color Grayish black
Crystal habit Massive, rarely as tetrahedral crystals, as incrustations
Crystal system Cubic
Twinning Common as lamellae on {111}
Cleavage None
Fracture Subconchoidal
Tenacity Brittle
Mohs scale hardness 3
Luster Metallic
Streak Black
Diaphaneity Opaque
Specific gravity 7.7 - 7.8
References [1][2][3]

Metacinnabar is the cubic form of mercury sulfide (HgS). It is the low temperature form and trimorphous with cinnabar (trigonal structure) and the high temperature hypercinnabar (hexagonal structure). It occurs with cinnabar in mercury deposits and is associated with native mercury, wurtzite, stibnite, marcasite, realgar, calcite, barite, chalcedony and hydrocarbons.[1]

It was first described in 1870 for an occurrence in the Redington mine, Knoxville, Napa County, California.[2][3]