MineralsMinerals are the natural chemicals from which rocks are made.
All but a few minerals are crystals. Some rocks are made from crystals of just one mineral; many are made from half a dozen or more minerals.
Most minerals are combinations of two or more chemical elements. A few minerals, such as gold and copper, are made of just one element. There are over 2000 minerals, but around 30 of these are very common. Most of the less common minerals are present in rocks in minute traces. They may become concentrated in certain places by geological processes.
Silicate mineralsSilicate minerals are made when metals join with oxygen and silicon. There are more silicate minerals than all the other minerals together.
Silicates and quartzThe most common silicates are quartz and feldspar, the most common rock-forming minerals. They are major constituents in granite and other volcanic rocks The Earth’s surface contains an enormous wealth of mineral resources, from clay for bricks to gems such as rubies and diamonds.
Fossil fuelsFossil fuels are oil, coal and natural gas. Fossil fuels were made from the remains of plants and animals that lived millions of years ago. The remains were changed into fuel by intense heat and pressure.
CoalCoal is made from plants that grew in swamps during the Carboniferous Period 300 million years ago.
Oil and natural gasOil and natural gas were made from the remains of tiny plants and animals that lived in warm seas.
OresOres are the minerals from which metals are extracted.
Bauxite is the ore for aluminium;
chalcopyrite for copper;
galena for lead;
hematite for iron;
sphalerite for zinc.
Veins of mineralsVeins are narrow pipes of rock that are rich in minerals such as gold and silver. They are created when hot liquids made of volcanic material uncracks in the rock.
Gems and crystals
|Gems and crystals|
Less rare gems are known as semi-precious gems. Gems are weighed in carats. A carat is one-fifth of a gram. A 50-carat sapphire is very large and very valuable. In the ancient world gems were weighed with carob seeds. The word ‘carat’ comes from the Arabic for seed.
Topaz Garnet Diamond Emerald Diamonds are among the oldest mineral crystals, over 3000 million years old. When magma cools, minerals with the highest melting points crystallize first.