Rare. Second and third oxidation zones.
- 2nd Oxidation Zone
- 3rd Oxidation Zone
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.).