If you are wondering how quickly the deterioration occurs, the answer is immediately, but fortunately very slowly. Ancient Chinese carvings of realgar are still in existence, but badly affected by the deterioration. The deterioration of realgar was thought to produce the closely related yellow orpiment , but this was recently proven to be false and the deterioration product is in fact yellow-orange pararealgar. In old paintings and manuscripts, realgar was a common pigment for paints and dyes. Many of these paintings now have a yellow or orange hue where once the color must have been an original red.
Color is orange to red.
Luster is resinous, adamantine to sub-metallic. Crystals are translucent to transparent. They are terminated by a wedge-like dome. Also found as grains, crusts and earthy masses. Cleavage is good in one direction.