What is "pararealgar"

n. (context mineralogy English) A crumbly arsenic sulfide material that forms gradually from realgar under exposure to light.

Pararealgar is an arsenic sulfide mineral with the chemical formula AsS also represented as AsS. It forms gradually from realgar under exposure to light. Its name derives from the fact that its elemental composition is identical to realgar, AsS. It is soft with a Mohs hardness of 1 - 1.5, is yellow orange in colour, and its monoclinic prismatic crystals are very brittle, easily crumbling to powder.

It is one of the sulfides of arsenic and is one of two isomers of AsS. It forms upon exposure of the symmetrical isomer to light. Its name derives from the fact that its elemental composition is identical to realgar, AsS.