Realgar: Gemstone Information
Realgar is ASS and forms striated red to orange-yellow prismatic crystals of the monoclinic system. The crystals when fresh are transparent with a greasy lustre but disintegrate to a powder after long exposure to light.The hardness is 1.5–2 and the SG 3.56. The RI for the alpha, beta and gamma rays is 2.538, 2.684 and 2.704, biaxial negative with birefringence 0.166. Gem-quality crystals have been found at the Getchell mine,Humboldt County, Nevada, and at locations in Washington state, especially at the Green River Gorge, Franklin, King county, USA.