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Formula: Rh(Cu1-xGex) x between 0 and 0.5
Alloy of rhodium, copper and germanium
Crystal system: Isometric
Specific gravity: 5.78 calculated for the empirical formula
Hardness: 5 for the synthetic analogue
Colour: Silver-grey
Environments
Michitoshiite-(Cu) is a relatively new mineral, approved in 2019 and to date (July 2025) reported only from
the type locality.
Localities
The type Locality, Haraigawa, Misato, Shimomashiki District, Kumamoto Prefecture, Japan, is a
platinum group mineral
placer deposit, most of which is composed of
isoferroplatinum-based grains, with the grain surface often
altered to tulameenite or
tetraferroplatinum. Such
isoferroplatinum-based grains are characterised by many inclusions
and nubs. The nubs consist mainly of laurite,
erlichmanite,
cuprorhodsite,
ferrotorryweiserite and
shiranuiite. The
cuprorhodsite- and
shiranuiite-based nub originates from
bowieite, which is the second most common inclusion in the
isoferroplatinum-based grains.
Ferrotorryweiserite also may be derived from
bowieite, because it occurs as a nub and has the same
rhodium-dominant character as
cuprorhodsite and
shiranuiite. Michitoshiite-(Cu) occurs in association with
cuprorhodsite-,
Ferrotorryweiserite, or
shiranuiite-based nubs. In its most common occurrence,
michitoshiite-(Cu) forms the outermost layer of a
cuprorhodsite-based nub associated with an
isoferroplatinum-based grain. It rarely occurs as a component
inside the nub in association with cuprorhodsite,
Ferrotorryweiserite or
shiranuiite. In this type of occurrence, michitoshiite-(Cu)
occurs along a crack in the aggregate.
Michitoshiite-(Cu) on the surface of the nub shows a silver-grey colour and pale grey with brownish tint in
reflected light. It occurs as fine anhedral grains up to 5 µm in size on the nub
(Bulletin of the National Museum of Nature and Science. Series C (Geology & Paleontology), 50.1-6).
Michitoshiite-(Cu) from Haraigawa -
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