Metacinnabar Locality: Mount Diablo Mine (Mt. Diablo Mine; Ryne Mine), Mount Diablo , Clayton , Contra Costa County , California , USA ( Locality at mindat.org ) Size: 6.5 x 4.5 x 3.0 cm. Metacinnabar is an uncommon mercury ore worldwide. Lustrous, complexly rounded, dark gray metacinnabar crystals to 5 mm richly cover the quartz-rich matrix plate from the Mt. Diablo Mine of California. Ex John Ydren Collection. Older material. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Metacinnabar
The cubic, high-temperature form of mercury sulfide — black rather than cinnabar's scarlet.
Intro adapted from Wikipedia (CC BY-SA).
Metacinnabar is an IMA-recognized mineral species in the sulfide class, with the chemical formula HgS.
It crystallizes in the cubic crystal system (space group F-43m). It is a member of the Sphalerite structural group.
Key properties: Mohs hardness 3; specific gravity 7.65; Black streak; Metallic luster.
IMA symbol Mcin, grandfathered status — known before the IMA’s founding, named in 1870.
Found in mercury deposits formed under low-temperature near-surface conditions.
It is found associated with Cinnabar, mercury, wurtzite, stibnite, marcasite, realgar, calcite, barite, “chalcedony”, hydrocarbons.
Its name comes from the Greek for with, plus cinnabar, in allusion to its common association.