Ores and Metallurgy
2.0 Classification of Ores
2.0 Classification of Ores
1. Native Ores: These ores contain the metal in free state and are found in the company of rock or alluvial impurities like clay, sand etc. Silver, Gold, Platinum, Mercury, Copper, etc. occur as native ores. Sometimes lumps of pure metals are also found known as nuggets.
2. Oxidised Ores: These ores consist of oxides or oxysalts (example. carbonates, phosphates, nitrates, sulphates, silicates etc.) of metals.
- Oxide ores are haematite ($Fe_2O_3$), bauxite ($Al_2O_3.2H_2O$), cassiterite or tin stone ($SnO_2$), cuprite ($Cu_2O$) and zincite ($ZnO$).
- Carbonate ores are limestone ($CaCO_3$), dolomite ($CaCO_3. MgCO_3$), calamine ($ZnCO_3$).
- Sulphate ores are Epsom salt or epsomite ($MgSO_4.7H_2O$), anhydride ($CaSO_4$), and anglesite ($PbSO_4$).
3. Sulphurised Ores: These ores consists of sulphides of metals like iron, lead, mercury etc. Examples are iron pyrites ($FeS_2$), Galena ($PbS$), Cinnabar ($HgS$).
4. Halide Ores: These ores consists of halides of metals. Examples are horn silver ($AgCl$), fluorspar ($CaF_2$), Mercuric chloride ($HgCl_2$) etc.