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Formula: Ag3SbS3
Sulphosalt, silver- and antimony-
bearing mineral, monoclinic paramorph of trigonal
pyrargyrite and
pyrostilpnite
(also monoclinic, and stable only below about 192°C)
Crystal System: Monoclinic
Specific gravity: 5.809 calculated
Streak: Orange
Colour: Orange
Environments
Metamorphic environments
Hydrothermal environments
Pyradoketosite is a new mineral, approved in 2020 and to date (May 2023) reported only from the type
locality.
Localities
At the type locality, the Sant'Olga tunnel, Monte Arsiccio Mine, Sant'Anna di Stazzema, Stazzema, Lucca Province,
Tuscany, Italy, pyradoketosite was discovered in the pyrite +
baryte + iron oxide ore deposit. It occurs
as brittle orange acicular crystals, up to 200 μm in length and 25 μm in thickness, with adamantine lustre. Under
reflected light, pyradoketosite is slightly bluish grey, with abundant orange internal reflections.
Pyradoketosite is associated with pyrargyrite,
tetrahedrite-(Hg),
valentinite, and probable
pyrostilpnite in baryte +
dolomite + quartz veins embedded in
metadolostone. Its name derives from the old Greek words “πυρ” (fire)
and “άδόκητος” (unforeseen), because of the unexpected occurrence of this third polymorph of the compound
Ag3SbS3
(AM 107.1901–1909).
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