2. 6.1 Minerals in the Earth’s Crust
• Rocks are made up of minerals found in the Earth’s crust
• Mineral: any solid element or compound that is found
naturally in the Earth’s crust
• Examples of minerals: gold, limestone (calcium carbonate),
silver and etc.
3. • Minerals exist in the form of natural elements
or natural compounds.
• Only a small amount of minerals exist in the
earth’s crust as natural elements.
• Eg of natural elements: gold, silver, platinum
• Most of the minerals exist in the form of
natural compounds
• Eg: oxides, sulphides, carbonates and silicates
4. Elements present in minerals that are
found as natural compounds
Natural compound Mineral Elements
Oxide Haematite Iron, oxygen
Cassiterite Tin, oxygen
Carbonate Calcite Calcium, oxygen. Oxygen
Malachite Copper, carbon, oxygen
Sulphide Iron pyrite Iron, sulphur
Galena Lead, sulphur
Silicate China clay Aluminium, silicon, oxygen
Calcium silicate Calcium, silicon, oxygen
5. Properties of minerals
• Each of the mineral has its own properties.
• Different composition of minerals generally
possess the following properties:
– Hardness
– Solubility in water
– Effect of heat
6. Hardness of minerals
• Generally, minerals are hard
• All mineral oxides, sulphides and carbonates
are hard but the hardest mineral is the
diamond
7. Solubility of minerals in water
• Most minerals are insoluble in water
• Only oxides, sulphides and carbonates of
potassium and sodium are soluble in water.
8. Action of heat on minerals
Metal oxides
• Most metal oxides are stable in high
temperature.
• They do not break down when heated
Metal sulphides
• When heated, sulphides break down to metal
oxides and sulphur dioxide is released.
heated
Metal sulphide metal oxide + sulphur dioxide
9. Metal carbonates
• When heated, carbonates break down to
metal oxides and carbon dioxide is released.
• The carbon dioxide produced turns limewater
cloudy.
heated
Metal carbonate metal oxide + carbon dioxide
