Formula: Al6(Se4+O3)3[SiO3(OH)](OH)9.10H2O
Selenite, a polyoxometallate
Crystal System: Orthorhombic
Specific gravity: 2.27 measured, 2.32 calculated for the empirical formula
Hardness: 2 to 2½
Streak: White
Colour: Colourless

Sedimentary environments
Hydrothermal environments

Petermegawite is a new mineral, approved in 2021 and to date (October 2023) reported only from the type locality.


At the type locality, El Dragón mine, Porco Municipality, Antonio Quijarro Province, Potosí, Bolivia, petermegawite was found associated with cobalt-bearing krut′aitepenroseite (matrix), chalcomenite, clinochalcomenite (unapproved, but probably valid), molybdomenite, lepidocrocite, goethite, ahlfeldite and calcite.
The mine exploited a telethermal deposit (a hydrothermal mineral deposit formed at shallow depth and relatively low temperatures) consisting of a single selenide vein hosted in sandstone and shale. The major ore mineral is krut′aite, which ranges in composition to penroseite. Late-stage fluid, rich in bismuth, lead and mercury, resulted in the crystallisation of minerals such as clausthalite, petrovicite, watkinsonite, and the recently described minerals eldragónite, grundmannite, hansblockite, cerromojonite and nickeltyrrellite. Oxidation produced a wide range of secondary selenium-bearing minerals, such as favreauite, alfredopetrovite, bernardevansite (dimorphous with alfredopetrovite), franksousaite, and the new mineral petermegawite.
Petermegawite occurs as aggregates of bladed or tabular crystals, with individual crystals up to 0.15 x 0.08 x 0.03 mm3 (CJMP 61.987-998).

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