Type Locality

Formula: CuI

Occurrence: Very Rare

Named after Australian C.W. Marsh who first described the mineral.

ColourColourless or pale yellowish when fresh. Darkens to salmon-pink to brownish-red on exposure.
LustreSub-Adamantine, Greasy
Crystal SystemCubic
FluorescenceBright red under longwave UV

Usually occurs as tetrahedral crystals that can alter colour upon prolonged exposure. Highly fluorescent. Many previously unknown marshite specimens have been “discovered” since the arrival of the Convoy-type UV torches.

Cuprite is the most common associate.