Cassiterite is an important ore of tin, with the chemical formula $\mathrm{Sn}{O}_2$. The extraction of tin from cassiterite primarily involves carbon reduction, as tin is less reactive and can be reduced by carbon.

Step 1: Concentration of the Ore
The ore is crushed and concentrated by gravity separation or froth flotation to remove impurities like silica, iron oxides, and other gangue materials.

Step 2: Roasting
The concentrated ore is roasted in air to oxidize any sulphide impurities (if present) to their oxides and to remove volatile impurities.

Step 3: Reduction
The main step is the reduction of tin oxide with carbon (coke or coal) in a reverberatory furnace. The reaction is: $\mathrm{Sn}{O}_2+2C\to \mathrm{Sn}+2\mathrm{CO}$ This is a carbon reduction process for an oxide ore.

Step 4: Purification
The crude tin obtained may contain impurities like iron, copper, lead, etc. It is purified by liquation (using the lower melting point of tin) or electrolytic refining.

Thus, the extraction of tin from cassiterite involves carbon reduction of an oxide ore.

Related Topics

Carbon Reduction: Used for metals like Zn, Fe, Sn, Pb, etc., which are less electropositive and can be reduced by carbon. The reducing agent is coke or coal.

Self-Reduction: Used for certain sulphide ores (e.g., copper pyrites) where part of the sulphide ore acts as a reducing agent. Not applicable here.

Removal of Impurities: Iron and copper impurities are removed during purification, but this is not the primary extraction step.

Important Formulae

Reduction reaction: $\mathrm{Sn}{O}_2+2C\to \mathrm{Sn}+2\mathrm{CO}$