Siderite: Gemstones Information

Siderite is Fe2CO3 and forms translucent yellow-brown rhombohedral to steep scalenohedral crystals in the trigonal system with hardness 3.5–4.5 and one direction of perfect cleavage. The SG is 3.83–3.96 and the RI for the ordinary and extraordinary rays is 1.875 and 1.633, uniaxial negative with birefringence 0.240. Siderite occurs in sedimentary deposits and hydrothermal ore veins. Large brown rhombs are found at Mt Saint Hilaire, Quebec, Canada.Orange and pinkish orange specimens from this locality show weak absorptions at 520–510 nm, 485 and 450 nm and brown transparent crystals have been found at the Morro Velho gold mine, Nova Lima, Minas Gerais, Brazil. Some facet-quality specimens are reported from Panasqueira,Portugal.