SULFIDES; SIMPLE SULFIDES · ISOMETRIC

Metacinnabar

HgS

Hardness: 3
Streak: Gray to black
Spec. Gravity: 7.7–8.1
System: Isometric

About

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.

Crystal Forms & Aggregates

In small and usually distorted equant crystals in the form of complex tetrahedral and pyritohedral forms. Crystals are sometimes rounded and usually striated. Also platy, in small crystal clusters, in rounded balls, and encrusting.

Striking Features

Crystal habits, color, and mode of occurence.

Environment

In volcanic, mercury-rich deposits usually associated with hot springs, and in epithermal veins.

Varieties

✓ common · ✗ uncommon

Onofrite— Selenium-rich variety of Metacinnabar, with selenium partially replacing the sulfur. Described from San Onofre, Plateros, Zacatecas, Mexico.

Polymorphs

Cinnabar, Hypercinnabar

Uses

As a minor ore of mercury in mercury deposits.

Noteworthy Localities

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

Distinguishing Similar Minerals

Sphalerite - Lower specific gravity, brown streak.

Photos

Crystal forms

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Complex Tetrahedral

Metacinnabar

Abouti

Crystal Forms & Aggregatesi

Striking Featuresi

Environmenti

Varietiesi