Stibnite is an important antimony mineral ore that is composed of Sb2S3. It contains 71.4% antimony and has long columnar or acicular crystals. Its crystals belong to the orthorhombic system, and the crystal surfaces have longitudinal stripes and are usually tarnished. The aggregates are often radiating or granular. Its colour and streaks are lead-grey. It has opaque diaphaneity, a metallic lustre, a specific gravity of 4.63–4.66, a Mohs hardness of 2 and a low melting point (550 °C). It is a low-temperature hydrothermal mineral and often forms with realgar, orpiment and cinnabar. It is an important raw material for antimony smelting. It can also be crafted into excellent ornamental stones.