Valentinite occurs as a weathering product of stibnite and other antimony minerals. Bismuth(III) sulfide is isostructural with SbS, stibnite. It occurs in low-temperature hydrothermal veins associated with cinnabar, stibnite, sulfur and gypsum. It occurs in association with cervantite, valentinite, kermesite, native antimony and stibnite. The ore is composed of quartz, calcite, stibnite and some pyrite. In geology, the mineral stibnite, SbS, is sometimes called antimonite. Thiourea has been implemented commercially for ores containing stibnite. It occurs as a secondary alteration product of other hydrothermal antimony minerals such as stibnite. Many antimony ores are sulfides, including stibnite (), pyrargyrite (), zinkenite, jamesonite, and boulangerite. The antimony mineral stibnite may have been a component of Greek fire. It occurs associated with stibnite, native antimony, stibiconite, cervantite, kermesite and tetrahedrite. Pyrite, stibnite, orpiment and realgar are the main minerals forming the ore. Small deposits of stibnite are common, but large deposits are rare. Pliny incorrectly wrote that stibnite would give lead on heating, instead of antimony. The "antimony" here was in fact stibnite, antimony-sulfide (SbS).