Scorodite

Scorodite


Composition: Fe3+AsO4 2H2O
Crystal System : Orthorhombic
Colours: Pale greyish-green, dark green, yellow-brown, blue, bluish-green
Lustre : Adamantine, vitreous
Hardness (H) : 3.5-4.0
Specific Gravity (S.G) : 3.28
References: Gebhard (1999)

Distribution

Rare. Second and third oxidation zones.

Occurrence

  • Supergene
  • 2nd Oxidation Zone
  • 3rd Oxidation Zone

Notable Finds

On 30 Level, as thick-bladed, gemmy, blue pseudo-octahedral crystals to 50 mm, with powellite and betpakdalite-CaCa. On 35 Level, again as gemmy blue crystals with the type assemblage for betpakdalite-CaMg. Also found in the third oxidation zone as crystals to 20 mm, with rare associates wilhelmkleinite and gertremmelite.

Paragenetic and General Notes

Scorodite occurs at Tsumeb as well-formed, gemmy blue crystals to 50 mm in length.  Pseudo-octahedral crystals are common. Lustre varies from adamantine to "frosted" (Pinch and Wilson, 1977). 

Tsumeb scorodite exhibits a striking "alexandraite"-like colour-change effect, showing bluish-green in daylight to bluish-purple in incandescent light (Gebhard, 1999).

Gallium-rich (pale-blue) and aluminium-rich (light greenish-blue, or green) varieties of scorodite also occur. The aluminium-rich variety is from the deeper levels of the third oxidation zone, and exhibits a different colour change, from greenish-blue in natural light, to a "phosphorescent green" in artificial light (Gebhard, op.cit.).