Arsenolite
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Arsenolite is an arsenic mineral, chemical formula As₄O₆. It is formed as an oxidation product of arsenic sulfides. Commonly found as small octahedra it is white, but impurities of realgar or orpiment may give it a pink or yellow hue. Wikipedia
Color: White, pale blue, pink to pale yellow if impure
IMA symbol: Aso
Optical properties: Isotropic; may be anomalously anisotropic