Realgar

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Realgar is a mineral consisting of arsenic monosulfide (α-As4S4). Its composition in weight is: 70.03% arsenic and 29.97 % sulphur and its molecular weight is 106.9.

Realgar has a red to yellow color and is often found among other arsenic minerals, less often with silver and lead ores. Its crystal structure is monoclinic, showing short prismatic crytals. Under a prolonged exposure to light it disintegrates to a powder which long was thought to be orpiment, but in fact is the polymorph pararealgar.[1] . Realgar when heated forms yellow arsenic, a poisonous oxide used in metallurgy.

The name is from the Arabic, ''rahj al-ġār [powder of the mine].

Reference

  1. ↑ P. Bonazzi, S. Menchetti, G. Pratesi, The crystal structure of pararealgar, American Mineralogist , vol. 80, pp. 400-403 (1995) pdf
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