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Cerargyrite Mineral Facts:

Chemical Formula: AgCl
Silver chloride consists of 24.7 per cent chlorine and 75.3 per cent silver, but cerargyrite often contains, in addition to its essential constituents, some mercury, bromine and occasionally some iodine.

Colors: White, gray, yellowish, sometimes colorless.

Hardness: 1 to 1.5
Hardness varies somewhat depending on porosity. Often sectile, and can be cut with a knife like horn.

Density: 5.5
For both the density and hardness reading for aragonite are higher than normally found for calcite.

Cleavage: Crystals are rare, usually found in a massive form, resembling wax; often in plates and crusts.

Crystallography: Isometric with cubic habit

Luster:. Waxy, massive, Vitreous, transparent to translucent, white streak.

Optics: (Refractive Index)  2.07
 

Composition, Structure and Associated Minerals:
Cerargyrite is an important secondary silver ore. It is only to be found in the upper, enriched zone of silver veins where descending waters containing small amounts of chlorine have acted upon the oxidized products of the primary silver ores of the vein. It is found associated with other silver ores, galena, etc. and sometimes with  native silver, cerussite and secondary minerals in general. The mineral is sometimes found massive, embedded among other minerals, but is more frequently in crusts covering other substances.

Outside the US, the most important localities for cerargyrite are the silver mines of Peru, Chile, Honduras and Mexico, where it is associated with native silver. It was also mined in the silver mines of Saxony in Europe.

Identification and Diagnostics
Cerargyrite is easily distinguished from all other minerals, except the comparatively rare bromide and iodide, by its physical properties and by the metallic globule which it yields on charcoal. On exposure to light it quickly turns violet-brown. It is usually associated with other silver compounds, the mixture being mined and smelted without separation of the components. It is usually recognizable by its waxy, massive character.
 

Testing for the presence of Silver:
In the closed tube cerargyrite fuses without decomposition. On charcoal it yields a metallic globule of silver, and when heated with oxide of copper in the blowpipe flame it gives the chlorine reaction. The mineral is insoluble in water and in nitric acid but is soluble in ammonia, and potassium cyanide. When a particle of the mineral is placed on a sheet of zinc and moistened with a drop of water, it swells, turns black and is finally reduced to metallic silver, which, when rubbed by a knife blade, exhibits the white luster of the metal.

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