Hypercinnabar

hypercinnabar

metacinnabar

cinnabar

mercury

Images

Formula: HgS
Sulphide, hexagonal paramorph of trigonal cinnabar and isometric metacinnabar
Crystal System: Hexagonal
Specific gravity: 7.43 measured, 7.54 calculated
Hardness: 3
Streak: Dark black-purple
Colour: Black with purple cast
Environments

Sedimentary environents
Hydrothermal environents

Hypercinnabar is the high-temperature phase of mercury sulphide, HgS. It shows a slight deficiency in mercury. It occurs in sulphide/arsenide/selenide veins intimately associated with metacinnabar, which it generally resembles (HOM, Mindat).
In a synthetic sample, heated in a sealed container, the initial pseudocubic metacinnabar phase partially transforms to a previously unknown phase (XHgS) in the temperature range 194^oC to 249^oC. This phase disappears at 254^oC, and the metacinnabar phase changes to a well crystalline cubic phase; cinnabar develops at 269^oC. The proportion of cinnabar continues to increase up to 374^oC. At higher temperature (475^oC), there is evidence for a partial phase transition to the high temperature hypercinnabar HgS structure. No phase transitions were observed for a natural cinnabar sample (MM 74.1.85–96).

Localities

The type locality is the Mount Diablo Mine, Mount Diablo, Clayton, Contra Costa county, California, USA.

Phase relations in the mercury-sulphur system (AM 63.1146)

S: sulphur
Hg: mercury
cn: cinnabar
mcn: metacinnabar
hcn: hypercinnabar



















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