Pararealgar

Description

An orange-yellow Arsenic sulfide mineral that can occur as a light induced alteration product of Realgar. Pararealgar has been found in association with realgar in occasional classical artwork, as well as southeast Asian and European paintings. Orange realgar will convert to yellow pararealgar on exposure to light. The differences phases of Orpiment, realgar and pararealgar can be distinguish with Raman spectroscopy.

Synonyms and Related Terms

arsenic sulfide

Risks

• Highly toxic by ingestion and inhalation.
• Carcinogen and mutagen

Physical and Chemical Properties

• Composition = AsS or As2S2
• Mohs Hardness = 1.0-1.5
• Density = 3.52 g/ml
• Refractive Index = >2.02
• Monoclinic, yellow, prismatic crystals.
• Fracture=brittle and uneven
• Luster=vitreous to resinous.
• Pigment particles are irregular with high relief.

Resources and Citations

• Ruth Siddall, 'Mineral Pigments in Archaeology: Their Analysis and the Range of Available Materials' Minerals Vol 8, p. 201 (2018). Link
• K. Trentelman, L. Stodulski, M. Pavlosky, 'Characterization of pararealgar and other light-induced transformation products from realgar by Raman microspectroscopy' Analytical Chemistry 68 (1996) 1755-1761.
• Webmineral: Pararealgar
• Nicholas Eastaugh, Valentine Walsh, Tracey Chaplin, Ruth Siddall, Pigment Compendium, Elsevier Butterworth-Heinemann, Oxford, 2004
• Wikipedia: Pararealgar Accessed March 2025