Mineral Species: Pararealgar

Chemical Formula: As4S4

Chemical Name: Arsenic Sulphide

Mineral Class: Sulphide

Mineral Notes: Pararealgar is an alteration product of Realgar in stibnite-bearing quartz veins, the alteration typically a result of exposure to light. It is trimorphous with Alacranite and Realgar, which means all three have the same chemical composition but different crystal structure. It is thought that light breaks As-As bonds, which are weaker than As-S bonds, and that the resulting structure forms a three dimensional, largely covalent lattice, in which free As atoms are intercalated.

Description: Crystals of orange-red Pararealgar on a white matrix. The fact that the mineral is crystalline is very rare because the vast majority of specimens are amorphous crusts or coatings. In addition the mineral has a very attractive waxy luster.

Location: Lengenbach Quarry, Binntal, Valais, Switzerland.