Alarsite, formula- (AlAsO4) is an aluminum arsenate mineral with its name derived from its composition: aluminum and arsenate. It is a trigonal mineral. It occurs as brittle subhedral grains which exhibit trigonal symmetry. It has a Mohs hardness of 5-5.5 and a specific gravity of 3.32. It is semitransparent, colorless with pale yellow tints and shows a vitreous luster. It is optically uniaxial (+) with refractive indices of nω = 1.596 and nε = 1.608.

General information

  • Formula: AlAsO4
  • Color: Colorless, with pale tints of yellow, green, blue due to inclusions.
  • Lustre: Vitreous
  • Hardness: 5 – 5½
  • Specific Gravity: 3.32 (Calculated)
  • Crystal System: Trigonal

It was reported from fumaroles in the Tolbachik volcano, Kamchatka, Far Eastern Region, Russia. It occurs in association with fedotovite, klyuchevskite, lammerite, nabokoite, atlasovite, langbeinite, hematite and tenorite.

Physical Properties of Alarsite

  • Lustre: Vitreous
  • Transparency: Transparent, Translucent
  • Comment: colorless in transmitted light
  • Streak: White
  • Hardness: 5 – 5½ on Mohs scale
  • Tenacity: Brittle
  • Cleavage: None Observed
  • Density: 3.32 g/cm3 (Calculated)


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