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Formula: Zn2CuGaS4
Sulphide, stannite group,
zinc- and
gallium- bearing mineral
Crystal System: Tetragonal
Specific gravity: 4.278 calculated
Hardness: 3
Streak: Black
Colour: Dark grey
Environments
Pegmatites
Hydrothermal environments
Richardsite was approved in 2019 and to date (January 2023) 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
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
(https://www.mindat.org/click.php?enc=aHR0cHM6Ly93d3cubWRwaS5jb20vMjA3NS0xNjNYLzEwLzUvNDY3L3BkZg%3D%3D).
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