Formula: As2O3
Simple oxide of arsenic, paramorph of claudetite
Crystal System: Isometric
Specific gravity: 3.86 to 3.88 measured, 3.88 calculated
Hardness: 1½
Streak: White to pale yellowish white
Colour: White, bluish; reddish to yellowish if impure with realgar or orpiment; colourless in transmitted light
Solubility: Slightly soluble in hot water

Hydrothermal environments
Coal-seam fires

Arsenolite is an oxidation product of other arsenic-bearing sulphides in hydrothermal veins, and it also may be formed in mine fires or in burning coal seams. (Dana, HOM). Associated minerals include claudetite, realgar, orpiment and erythrite (HOM).

At Rauenthal, Haute-Rhin, France, arsenolite forms as a direct oxidation product on native arsenic (Dana).

At Sorbier, Loire, France, arsenolite forms from burning coal dumps (Dana).

At Andreasberg, Hartz, Germany, arsenolite is found as an alteration product of skutterudite and other arsenides (Dana).

At the type locality,St Andreasberg, Braunlage, Goslar District, Lower Saxony, Germany, arsenolite occurs as an oxidation product of arsenic-bearing sulphides in hydrothermal veins (Mindat).

At the Lauta mine, near Marienberg, Saxony, Germany, arsenolite forms as an alteration product of arsenic (Dana).

At Bou Azzer, Morocco, arsenolite occurs in strongly weathered ores associated with erythrite, and with cobaltkoritnigite at Aghbar (MinRec 38.5.360).

At Morococha, Peru, arsenolite is associated with realgar and orpiment (Dana).

At the exchequer and Monitor mines, Alpine county, California, USA, arsenolite formed as an alteration product of enargite (Dana).

At the White Caps mine, Nye county, Nevada, USA, arsenolite formed from the burning of the shaft (Dana).

At the Ophir mine, Storey county, Nevada, USA, arsenolite forms as an alteration of native arsenic (Dana).

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