Metacinnabar

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

It was first described in 1870 for an occurrence in the Redington mine, Knoxville , Napa County, California