Hydroxide of gallium, söhngeite group
Specific gravity: 3.84 measured
Hardness: 4 to 4½
Colour: Brown, white, pale yellow, pale brown, pale greenish yellow
Söhngeite is a rare mineral; although it was approved in 1965, to date (July 2022) it has been reported only
from the type locality.
At the type locality, the Tsumeb Mine, Tsumeb, Oshikoto Region, Namibia, söhngeite generally forms aggregates on oxidising massive sulphide ore (galena, chalcocite, sphalerite) that is enriched in germanium and gallium, usually with significant content of germanite, renierite and gallite. It is an alteration product of gallite-bearing germanite in an oxidation zone of a dolostone-hosted hydrothermal polymetallic ore deposit, and forms crystalline, twinned groups and aggregates, up to 1 cm in size; single crystals are very rare. Associated minerals include germanite, gallite, calcite, quartz, siderite and tsumgallite (R&M 97.2.183, HOM, Mindat).
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