Realgar, also known as Ruby Sulphur or Ruby of Arsenic, is a toxic arsenic sulfide mineral that crystallizes in the form of grains, tabular crystals, and masses. The color can range from a bright red, to a soft yellow. Over time, when exposed to light, Realgar loses its pigment and changes form into another mineral known as Pararealgar. You will almost always find Orpiment growing with Realgar. It can also be found alongside Quartz, Calcite, Barite, and Galena.
