Stibnite

Stibnite is a mineral. Its chemical formula is Sb₂S₃. It is the main ore of antimony. The American Museum of Natural History has a huge crystal of stibnite. Stibnite is soft, with a Mohs hardness of 2. Its specific gravity is 4.63.

Stibnite

Uses

Historical

Stibnite was used to make kohl, a type of eyeliner. Use of stibnite in cosmetics dates to Ancient Egypt.^[source?]

Ore of antimony

Stibnite is the primary ore used to make elemental antimony. In most smelting processes, stibnite is heated with oxygen from the air to produce antimony trioxide and sulfur dioxide:^[1]

2 Sb₂S₃ + 9 O₂ → 2 Sb₂O₃ + 6 SO₂

The antimony dioxide is then treated with a strong reducing agent like carbon monoxide to yield the purified antimony metal:

Sb₂O₃ + 3 CO → 2 Sb + 3 CO₂