Which mineral is the chief ore of tin, with the chemical formula SnO₂?

Cassiterite is the chief ore of tin and has the chemical formula SnO₂.

It is a tin oxide mineral that commonly forms in hydrothermal veins associated with granitic rocks. Cassiterite can also accumulate in alluvial, or placer, deposits because its high density allows it to survive weathering and become concentrated in river sediments. Important deposits occur in parts of Southeast Asia, South America, Africa, and Cornwall in England.

The mineral is usually black, brown, reddish-brown, or colorless, and its name comes from the Greek word kassiteros, meaning tin. Tin is extracted from cassiterite by reducing the oxide in a furnace, producing metallic tin.

Cassiterite is sometimes confused with similarly dark ore minerals such as wolframite, which is a major tungsten ore, or with stannite, a copper-iron-tin sulfide. Cassiterite remains the principal mineral source of tin used in solder, coatings, alloys, and electronic manufacturing.