Class : Halides
    Subclass : Chlorides
    Crystal system : Cubic
    Chemistry : AgCl
    Rarity : Uncommon

Chlorargyrite (or cerargyrite) is a fairly common silver halide that sometimes forms abundantly in the oxidation zone of silver deposits in arid regions. It forms a complete solid solution with bromargyrite and usually occurs in "horny", waxy, sometimes columnar, rarely fibrous masses. It owes its name to its chemical composition : chlorine and silver (arguros in Greek). Chlorargyrite is translucent, resinous to adamantine in luster, pearl gray to grayish green in color, most often ; photosensitive, it becomes purple-brown then black in the light. The crystals are cubic or octahedral, often in sub-parallel groupings. Of low hardness (1.5 to 2.5), chlorargyrite is plastic and cuts into chips like wax. It is unalterable in air and remains stable in outcrops, often in the company of native silver, argentite and various metallic oxides. Chlorargyrite, unlike other silver halides, once existed in considerable quantities in outcrops and may thus have constituted an important silver ore. Large quantities of chlorargyrite have in fact been exploited in several deposits : Potosi (Bolivia), where Pone de Léon (1547) speaks of 6000 furnaces treating cerargyrite by fusion ; Johanngeorgenstadt and Schneeberg, in the Erzgebirge of Saxony ; Chañarcillo and Caracoles (Chile) ; finally, more anecdotally, at Treasure Hill (Nevada), where a 6-ton mass of chlorargyrite was extracted.

Main photo : Chlorargyrite from Broken Hill, Australia © Chris Stefano

Twins are common on {111} but rarely visible.

No fake identified for this mineral species.