Realgar is a sulfide of arsenic. This mineral is as called, “ruby of arsenic" or "ruby sulfur". It is malleable, ductile and frequently occurs as crystals in the monoclinic structure or in coarse, compressed, or powdery shape, along with the correlated mineral, Orpiment. It has an orange-red color and its melting point is 320 °C. On burning, it produces a flame of a bluish color, discharging fumes of sulfur and arsenic. It has an orange color streak. It has a similar morphology with Pararealgar and Alacranite.
As4S4 or AsS
Derivation of Name
It earns its name from “rahj”, Arabic word which means, “powder of the mine". It was first recorded in English during the 1390s.
Realgar is mostly found as a vein in hydrothermal formations at low-temperatures, coupled with other minerals like Antimony and Arsenic. It is also found in the deposits in hot springs and as volcanic sublimations. It is found in the company of Orpiment, Calcite, Arsenolite and Barite.
It is an awfully exceptional gem. It is especially soft and rather unstable.
It occurs with ores of silver, lead and gold in Saxony, Hungary and Bohemia. It is realized, particularly in Mercur, Utah; Nevada, Manhattan and among the Yellowstone geyser deposits in the U.S.
Realgar forms an oddity among sulfides. It is among the few sulfides which are not opaque, metallic or mildly colored. It possesses a structure similar to sulfur and looks like sulfur in nearly all respects, but for color (The name "ruby sulfur" has been used for Realgar). Structure of sulfur comprises of 8 sulfur atoms connected in a ring. The structure of Realgar alternates between arsenic and sulfur atoms, producing rings of As4S4. Arsenic atoms change the structure from sulfur's orthorhombic symmetry to Realgar's monoclinic symmetry.