Pyrargyrite
Pyrargyrite is an exceedingly rare collector’s gem. The chemical formula of Pyrargyrite is Ag3SbS3 and its molecular weight is 541.55 gm. Pyrargyrite crystals are found in several locations worldwide including Chile, Bolivia, Germany, Spain, Mexico, USA and Canada but are usually too small for faceting. Pyrargyrite has a specific gravity of 5.82 – 5.85 (g/cm3) and the refractive index of 2.881 – 3.084 Uniaxial ( – ). A limited quantity of large, transparent crystals have been found in Chile and Colquechaca, Bolivia. A few gems, some approaching 50 carats, have been cut from this material. However, these gems tend to be too dark to be very attractive.
| Category: | Sulfosalt |
| Chemical Formula: | Ag3SbS3 |
| Molecular Weight: | 541.55 gm |
| Crystallography: | Trigonal – Ditrigonal Pyramidal |
| Crystal Habit: | Crystals commonly prismatic, showing hemimorphism, typically with prominent development of rhombohedra; also steep scalenohedra, to 6 cm; massive, granular. Twinning: as twins of complex aggregates of individuals and as lamellar twins. |
| Cleavage: | [1011] Distinct, [0112] very Imperfect |
| Fracture: | Conchoidal to Uneven |
| Tenacity: | Brittle |
| Moh’s Hardness: | 2.5 |
| Density: | 5.82 – 5.85 (g/cm3) |
| Radioactivity: | Not Radioactive |
| Color: | Deep Red, Red Gray |
| Transparency: | Translucent to Opaque, darkens with exposure to light |
| Luster: | Adamantine to Submetallic |
| Refractive Index: | 2.881 – 3.084 Uniaxial ( – ) |
| Birefringence: | 0.2030 |
| Dispersion: | Weak to Distinct |
| Pleochroism: | Weak (distinct in air) |
| Anisotropism: | Strong; in pale yellow and gray-blue |
