Sulphide, stannite group, zinc- and gallium- bearing mineral
Specific gravity: 4.278 calculated
Colour: Dark grey
Richardsite was approved in 2019 and to date (July 2022) has been identified unambiguouly only on a specimen from
the type locality.
At the type locality, the Merelani Hills, Lelatema Mountains, Simanjiro District, Manyara Region, Tanzania, richardsite occurs on the faces of a cluster of dark orange-brown wurtzite–sphalerite crystals, to ~2.5 cm across, on a single known specimen from the gem mines. In addition to the primary wurtzite–sphalerite, associated minerals include a second generation of epitaxic sphalerite on the earlier wurtzite–sphalerite, grains of germanium- and gallium- rich wurtzite, minor hexagonal graphite crystals, and minor transparent, pale green crystals of diopside.
The order of crystallisation appears to be wurtzite–sphalerite → sphalerite → richardsite + germanium- and gallium- rich wurtzite → diopside + graphite
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