CHEMISTRY AsS Arsenic sulfide
CRYSTALLOGRAPHY Monoclinic
CRYSTAL GROWTH AND HABITS Realgar forms prismatic crystals with diamond shaped cross sections. Crystal terminations are often wedge shaped.
COLOR AND OTHER OPTICAL PROPERTIES Realgar is most commonly red to orange and is transparent to translucent.
HARDNESS 1.5 - 2
SPECIFIC GRAVITY 3.5 - 3.6
LUSTER Resinous to greasy
STREAK Orange red
BREAKABILITY Realgar has a good cleavage in one direction, conchoidal fracture and is brittle.
OCCURRENCE Realgar is found in low temperature hydrothermal veins with antimony sulfides. It is also found around fumaroles and as deposits in hot springs.
ASSOCIATED MINERALS Orpiment, arsenolite
NOTE 1: Arsenic is toxic so care must be taken to avoid contact with Realgar. Washing with soap and water is recommended as cleaning after contact with Realgar. Avoid contact with eyes and do not ingest.
NOTE 2: Realgar, upon long exposure to light, disintegrates to a light powder composed of arsenolite (an oxide) and orpiment.
NAME From the Arabic "rahj al ghar" meaning "powder of the mine".