Pyrargyrite

Pyrargyrite is silver antimony sulfide (Ag3SbS3), one of the silver sulfosalts and an important ore of silver. It crystallizes in the trigonal system and is famous as dark ruby silver, displaying deep red to ruby-red internal reflections, though surfaces often appear grayish-black.

Its name comes from Greek words for fire and silver, reflecting both its color and its silver content. It forms a closely related pair with proustite, the antimony analog of which (pyrargyrite) is darker, while the arsenic member (proustite) is brighter red.

Well-crystallized pyrargyrite is a classic and highly prized collector mineral, especially in fine prismatic crystals.

Pyrargyrite forms in hydrothermal silver veins, typically deposited at low to moderate temperatures in the later stages of mineralization, and as a secondary enrichment mineral in silver deposits.

It commonly occurs with native silver, acanthite, proustite, galena, and other silver and lead minerals in epithermal vein systems.

Classic localities include the silver districts of Mexico (Guanajuato, Zacatecas, Fresnillo), the Erzgebirge mines of Germany and the Czech Republic (Freiberg, Pribram), and Kongsberg in Norway. Mexican mines have produced superb crystallized specimens.

Pyrargyrite is identified by its deep red to grayish-black color with characteristic ruby-red internal reflections seen when light passes through thin edges, along with an adamantine to submetallic luster. Its streak is purplish-red, a key diagnostic, and it has a hardness of about 2.5.

The purplish-red streak and red internal color distinguish it from dark sulfides like acanthite and galena.

It closely resembles proustite, but proustite is a brighter scarlet (light ruby silver) with a more vivid red streak, whereas pyrargyrite is darker (dark ruby silver); pyrargyrite is also less light-sensitive than proustite.

Pyrargyrite is an important ore of silver and has contributed significantly to silver production in many historic mining districts. Silver recovered from such ores serves jewelry, coinage, electronics, and industrial uses.

Its greatest appeal today is as a mineral specimen: lustrous deep red prismatic crystals of pyrargyrite are classic, beautiful, and highly sought after by collectors.

Specimens should be protected from prolonged strong light, which can gradually darken silver sulfosalts. It contains antimony, so it should be handled sensibly, though it is valued mainly as an ore and specimen rather than for any metaphysical use.