Richardsite

richardsite

wurtzite

sphalerite

gallium

Images

Formula: Zn2CuGaS4
Sulphide, stannite group, zinc- and gallium- bearing mineral
Specific gravity: 4.278 calculated
Hardness: 3
Streak: Black
Colour: Dark grey
Environments

Pegmatites
Hydrothermal environments

Richardsite was approved in 2019 and to date (July 2022) has been identified unambiguouly only on a specimen from the type locality.

Localities

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 wurtzitesphalerite crystals, to ~2.5 cm across, on a single known specimen from the gem mines. In addition to the primary wurtzitesphalerite, associated minerals include a second generation of epitaxic sphalerite on the earlier wurtzitesphalerite, 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 wurtzitesphaleritesphaleriterichardsite + germanium- and gallium- rich wurtzitediopside + graphite
(https://www.mindat.org/click.php?enc=aHR0cHM6Ly93d3cubWRwaS5jb20vMjA3NS0xNjNYLzEwLzUvNDY3L3BkZg%3D%3D).

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