Calomel

HgCl

Hardness: 1–2
Streak: White
Spec. Gravity: 6.4–6.5
System: Tetragonal

About

Calomel is an uncommon mineral found in mercury deposits. It is one of the better-known mercury compounds, and may even be associated together with Native Mercury liquid droplets. Calomel is often found together with Cinnabar, the most common mercury compound, and may form as an alteration product of the Cinnabar.
Calomel derives its name from the Greek term "kalos", beautiful and "melos", black, in reference to its habit of turning black when coming into contact with ammonia.

Crystal Forms & Aggregates

Crystals may be tabular, prismatic, and sometimes pyramidal. Also in parallel skeletal growth, in small dense crystal groups, grainy and encrusting.

Other ID Marks

May be very strongly fluorescent with an orange to orange-red color.

Complex Tests

Turns black upon contact with ammonia.

Striking Features

Color and luster, occurrence in known mercury deposits, sectility, and strong fluorescence.

Environment

As a secondary mineral in mercury deposits.

Uses

Calomel is an ore of mercury.

Noteworthy Localities

Calomel is an uncommon mineral, found primarily in known mercury deposits. Some of the better known localities for this mineral include Landsberg, Rhineland-Palatinate, Germany; Terlingua, Brewster Co., Texas; and the Challenge deposit, Emerald Lake Hills, San Mateo Co., California.

Common Mineral Associations

Cinnabar, Mercury, Metacinnabar, Calcite, Terlinguaite, Eglestonite

Photos

Crystal forms

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Prismatic

Tabular

Pyramidal

Calomel

Abouti

Crystal Forms & Aggregatesi

Other ID Marksi

Complex Testsi

Striking Featuresi

Environmenti

Usesi

Noteworthy Localitiesi

Common Mineral Associationsi