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The Mineral metacinnabar

Metacinnabar on Quartz

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.

Chemical Formula

HgS

Color

Metallic gray

Crystal System

Isometric

Properties

Streak
Gray to black
Hardness
3
Transparency
Opaque
Specific Gravity
7.7 - 8.1
Luster
Metallic
Cleavage
None
Fracture
Uneven
Tenacity
Brittle to slightly sectile

Crystal Habits

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.

3D Crystal Atlas

Additional Information

Composition
Mercury sulfide
In Group
Sulfides; Simple Sulfides
Striking Features
Crystal habits, color, and mode of occurence.
Environment
In volcanic, mercury-rich deposits usually associated with hot springs, and in epithermal veins.
Rock Type
Igneous

Other Names

Metacinnabarite

Varieties

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

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

Distingushing Similar Minerals

Sphalerite - Lower specific gravity, brown streak.

metacinnabar Photos



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