Allargentum Locality: Harsted, Saxony, Germany Size: miniature, 3.2 x 2.7 x 1.4 cm Allargentum A fairly rare Silver-Antimony mineral, this specimen has well-defined crystals [Note: These formations are no crystals, but casts of the carbonate the allargentum is typically embedded in. - pH] interspersed with massive Allargentum, all on matrix. With such good metallic luster and actual crystals, this is a very fine specimen. Ex. Marilyn Dodge Collection. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Allargentum
Allargentum is a mineral from the class of antimonides, superclass of sulfides and sulfosalts (sometimes ascribed to the natural elements and alloys class), with formula written as Ag1−xSbx, where x = 0.09–0.16. This moderately rare mineral is found in silver ores and is therefore named from the Greek ἄλλος (allos, "another") and the Latin argentum ("silver"). Its Vickers hardness is 172–203.
Intro adapted from Wikipedia (CC BY-SA).
Allargentum is an IMA-recognized mineral species in the sulfide class, with the chemical formula Ag₁₋ₓSbₓ (x ≈ 0.09-0.16).
It crystallizes in the hexagonal crystal system (space group P6_3/mmc). It is a member of the Allargentum structural group.
Key properties: specific gravity 10; Metallic. Anisotropism: Weak. Bireflectance: Strong. R1 –R2: (400) 67.0–68.8, (420) 66.5–68.2, (440) 66.0–67.6 luster.
IMA symbol All, IMA status: approved, named in 1949.
Found in high-grade Ag–Sb ores.
It is found associated with Silver containing antimony and mercury, dyscrasite, breithauptite, domeykite, kutı́naite, stephanite.
Its name comes from the Greek for another and the Latin argentum, silver.