Formula: As₄S₄

Species:

Colour: Dark red to orange-red

Lustre: Resinous, Greasy

Hardness: 1½ – 2

Specific Gravity: 3.56

Crystal System: Monoclinic

Name: From Arabic “rahj al-gahr”, powder of the mine. Known as a mineral pigment in Byzantium (essentially Asia Minor and the Balkan Peninsula) at least by the beginning of the thirteenth century and presumably having a name by that time. An old realgar locality on the Balkan Peninsula is found at Allchar, Republic of Macedonia.

Alters to pararealgar on exposure to light. Visually similar to sarabauite and other red arsenic-sulphur minerals.