Stibnite, sometimes called antimonite, is a sulfide mineral with the formula Sb₂S₃. This soft grey material crystallizes in an orthorhombic space group. It is the most important source for the metalloid antimony. The name is from the Greek stibi through the Latin stibium as the old name for the mineral and the element antimony. As an antimony sulfide, it is potentially toxic and should be handled with care.