An oddball among the sulfides. It is one of only a few sulfides that are not metallic or opaque or blandly coloured. Similar to Sulphur apart from colour Realgar also called Ruby Sulphur. Sulphur has a structure composed of 8 Sulphur atoms linked in a ring. It’s structure alternates between Sulphur atoms and arsenic atoms producing rings of As4S4. The Arsenic atoms affect the structure altering it from Sulphur’s orthorhombic symmetry to Realgar’s monoclinic symmetry.
Occurs in hydrothermal veins with valuable metal Sulphide ores. The bright red colour can be an aid to prospectors. Also found in hot spring deposits and as a volcanic sublimate product (crystallizing from vapors). Gets its name from the Arabic words for “powder of the mine” (rahj al ghar). Famous for some wonderfully beautiful specimens. Some specimens can have a deep ruby red colour with an amazing clarity and a high luster. The color of Realgar is truly something to appreciate and cherish.