Black Sand Concentrates
It is usually a combination of minerals in the iron group: hematite, fe3o3, with a specific gravity of 5.26, an iron mineral that is non-magnetic and magnetite, fe3o4, with a specific gravity of 5.20, is magnetic. these black sands will weigh a third (1/3) to a fourth (1/4) the weight of gold (au). gold has a specific gravity of 15 to.