Fleetite

fleetite

ruthenium

iridium

osmium

Images

Formula: Cu2RhIrSb2
Antimonide containing rhodium and iridium
Specific gravity: 10.83 calculated
Colour: Light grey
Environments

Placer deposits

Fleetite seems to be the first mineral with rhodium Rh and iridium Ir positioned in separate structural sites rather than substituting for each other at a single site (Mindat). It is a relatively new mineral, approved in 2018 and to date (June 2022) reported only from the type locality.

Localities

At the type locality, the Miass River, Chelyabinsk Oblast, Russia, fleetite, a new species of platinum-group mineral, was discovered intergrown with an osmiumiridiumruthenium alloy in a placer. A single grain 50 μm across was found. Osmium, ruthenium and iridium are the main associated minerals; also present are platinum-iron alloys, laurite, antimony-rich irarsite, rhodium-rich tolovkite, kashinite, anduoite, ferronickelplatinum, heazlewoodite, platinum-group-element bearing pentlandite, and digenite, as well as micrometric inclusions of forsterite, chromitemagnesiochromite and magnesium-rich edenite.
Fleetite and other late exotic phases were formed by reaction of the associated alloy phases with a fluid phase enriched in antimony, arsenic and sulphur in circulation in the cooling ophiolite source-rock (CM 59.2.423–430).

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