It is a nonstoichiometric compound with a variable composition.

[2] Commercial samples are contaminated with sulfur, which may be removed by washing with carbon disulfide in a Soxhlet extractor.

It may be used as a red pigment and is one possible precursor to Schlippe's salt, Na3SbS4·9H2O, which can be prepared according to the equation: It is also used in the vulcanization of rubber to produce red rubber.

Like many sulfides, this compound liberates hydrogen sulfide upon treatment with strong acids such as hydrochloric acid.

[3] Analysis by Mössbauer spectroscopy indicates that this compound is a derivative antimony(III),[4] explaining the production of antimony(III) chloride, rather than antimony(V) chloride, upon acidification.