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The Mineral chlorargyrite

Chlorargyrite Crystal Mass

Chlorargyrite, despite being an important ore of silver, is not well-represented in collections. This is because of its general lack of aesthetics, with the bulk of mined material being processed for the extraction of its silver content. Formerly called Cerargyrite, Chlorargyrite is the currently accepted name of this mineral today. An old miners term describing this mineral was Horn Silver.

Chlorargyrite forms a solid solution series with Bromargyrite, which contains the halogen bromine instead of chlorine. Chlorargyrite and Bromargyrite can be visually indistinguishable from one another, and will often form in the same deposits. The intermediary mineral of this series, known as Embolite, is usually considered to be a bromine-rich variety of Chlorargyrite.

Chlorargyrite is named after its chemical composition: "chlor" for chlorine, and "argyros" for the Greek word used for silver. Chlorargyrite often darkens upon exposure to light, and specimens should generally be stored in the dark.

Chemical Formula

AgCl

Color

Light to dark gray, yellowish-brown to brown, yellowish-green, and butterscotch. Colorless when freshly exposed, but quickly oxidizes upon exposure to light.

Crystal System

Isometric

Properties

Streak
White

Hardness
1.5 - 2.5

Transparency
Transparent to translucent

Specific Gravity
5.5 - 5.6

Luster
Waxy, resinous, adamantine

Cleavage
None

Fracture
Uneven

Tenacity
Sectile and ductile

Crystal Habits

Individual crystals are uncommon, and usually limited to specific localities. They occur in cubic form, and in partially modified cubic or dodecahedral form. Crystals are usually grouped together in crystal aggregates. Most often encrusting, grainy, drusy, massive, and in thick, coral-like growths.

Additional Information

Composition
Silver chloride, sometimes with bromide and less commonly iodide

In Group
Halides

Striking Features
Color and luster, mode of occurrence, high specific gravity, and sectility.

Environment
As a secondary mineral in oxidation zones, forming in epithermal veins and hydrothermal replacement deposits of silver deposits.

Rock Type
Sedimentary

Other Names

	Cerargyrite
	Horn Silver

Varieties

Embolite

- Bromium-rich variety of Chlorargyrite; an intermediary mineral of the Chlorargyrite-Bromargyrite series.

Uses

Chlorargyrite is an important ore of silver. A handful of localities have produced material of interest, including visible crystals that make rare collector's items.

Noteworthy Localities

One of the most important localities of Chlorargyrite is the famous silver mine at Broken Hill, New South Wales, Australia. This locality has produced some of the best examples of this mineral, in a lightly-colored, bromium-rich type. In the 1980's, highly regarded collector's examples of this mineral were found in the Kintore open cut of that mine.

In the U.S., unusual cubic Chlorargyrite crystals were found De Lamar Mine, near Silver City, Owyhee Co., Idaho. This find is regarded by many to have produced the most well-crystallized examples of this mineral. Waxy brown coatings of Chlorargyrite have come from Calico, San Bernardino Co., California; and small greasy crystals from the Silver Coin Mine, Valmy, Humboldt Co., Nevada. Other locations in the Western U.S. include Leadville, Lake Co., Colorado; the Tintic District, Utah Co., Utah; and Bisbee and Tombstone, Cochise Co., Arizona.