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 Ag_1-xSb_x, where x = 0.09-0.16. This moderately rare mineral is found in silver ores and is therefore named from the Greek άλλος ("allos", another) and the Latin 'argentum' (silver). Its Vickers hardness is 172-203.