The Mineral metacinnabar
Metacinnabar is an uncommon polymorph of the mineral Cinnabar, forming in a different crystal system. In addition to its crystal forms, Metacinnabar also visually differs from Cinnabar, having a metallic luster, gray color, and lack of transparency.
Gray to black
7.7 - 8.1
Brittle to slightly sectile
Selenium-rich variety of Metacinnabar, with selenium partially replacing the sulfur. Described from San Onofre, Plateros, Zacatecas, Mexico.
As a minor ore of mercury in mercury deposits.
Metacinnabar is uncommon and there are sporadic occurrences in many of the important mercury deposits. The most significant locality of this mineral is Mount Diablo in the Diablo Range, Contra Costa Co., California.
Common Mineral Associations
Cinnabar, Dolomite, Quartz
Distingushing Similar Minerals
Sphalerite - Lower specific gravity, brown streak.