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Formula: SnGeS3
Sulphide of tin and germanium
Crystal System: Monoclinic
Specific gravity: 3.98 calculated
Hardness: 2
Streak: Very light yellowish
Colour: Orange to yellowish red
Luminescence: No fluorescence under 254 and 366 nm UV light was observed
Environments
Stangersite is a new mineral, approved in 2020 and to date (November 2023) recorded only from the type locality.
Localities
At the type locality, the Kateřina Coal Mine, Radvanice, Trutnov District, Hradec Králové Region, Czech Republic,
natural strangersite forms transparent, elastic and flexible flattened acicular crystals with cross-section
2–5 × 20–40 (μm)2 and up to 1 cm in length, which produce random or fan-shaped clusters on rock fragments
and on black crumbly ash; strangersite was also observed in multicomponent aggregates on which the acicular
crystals grow.
Phases of the strangersite-PbGeS3 series in these aggregates form irregular grains 2 to 100 μm in
size with a more variable composition. They exhibit an extensive solid solution between Pb and Sn limited to 70 mol%
Pb in the Sn position.
Strangersite formed under reducing conditions by direct crystallisation from hot gasses (250–300°C) at a depth
of 30–60 cm under the surface of a burning coal mine dump. It was found in close association with phases of the solid
solutions bismuth-antimony,
bismuthinite-stibnite and
bismuthinite-guanajuatite;
also with Bi3S2, Cd4GeS6,
herzenbergite, cadmoindite,
GeAsS and radvaniceite
(EJM 13.791-800).
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