Metacinnabar

Metacinnabar is the cubic form of mercury sulfide (HgS). It is the high temperature form and trimorphous with cinnabar (trigonal structure) and the higher 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.^[2]

Metacinnabar
General
Category	Sulfide mineral
Formula	HgS
IMA symbol	Mcin[1]
Strunz classification	2.CB.05a
Crystal system	Cubic
Crystal class	Hextetrahedral (43m) H-M symbol: (4 3m)
Space group	F43m
Unit cell	a = 5.8717(5) Å; Z = 4
Structure
Jmol (3D)	Interactive image
Identification
Color	Grayish black
Crystal habit	Massive, rarely as tetrahedral crystals, as incrustations
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	[2][3][4]

It was first described in 1870 for an occurrence in the Redington mine, Knoxville, Napa County, California.^[3][4]