SnGeS3 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; phases of the SnGeS3-PbGeS3 series, also occurring in the dump, exhibit an extensive solid solution between Pb and Sn limited to 70 mol. % Pb in the Sn position (Sejkora et al., 2001).
