Minerals(Gems,diamonds,Topaz)

Minerals

Minerals 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.

 

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 minerals 

 Silicate minerals are made when metals join with oxygen and silicon. There are more silicate minerals than all the other minerals together. 

Silicates and quartz 

The 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 fuels 

 Fossil 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. 

Coal 

Coal is made from plants that grew in swamps during the Carboniferous Period 300 million years ago.

 Oil and natural gas 

Oil and natural gas were made from the remains of tiny plants and animals that lived in warm seas.

 Ores 

 Ores 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 minerals

 Veins 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 are mineral crystals that are beautifully coloured or sparkling. There are over 3000 minerals but only 130 are gemstones. Only about 50 of these are commonly used. The rarest gems are called precious gems and include diamonds, emeralds and rubies. 

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. 

 Pegmatites

Unusual minerals are left behind to crystallize last, forming rocks called pegmatites. These rocks are often rich in gems such as emeralds, garnets, topazes and tourmalines. Some gems with a high melting point and simple chemical composition form directly from magma, such as diamond, which is pure carbon, and rubies. Gems often form in as bubbles called geodes in cooling magma. They can also form when hot magma packed with minerals seeps up through cracks in the rock to form a vein.There are more than 100 different kinds of gemstone.