Variety of Gemstones And Gems

Gemstones, also called as precious stones, are naturally available rare stones of earth. They get different names according to the chemicals present in them. Some important varieties of gemstones are diamond, corundum, beryl, coral and pearl.

Diamond is a precious stone made of pure carbon. It is allotrope form of carbon and noted for its hardness. The diamonds are white or pale yellow in colour. Less often they are also available in blue, green, yellow and black. Under the deep part of our earth, extreme pressure and temperature change carbon to glittering diamonds. Diamond's crystal system is cubic, hardness in Mohs scale is 10, refractive index is 2.4175, density is 3.5 gm/cc and melting point is 3,547 degree centigrade. About 26 tonnes of natural diamond is mined per year from all over the world. It is widely used in jewelry and optical industries.

These are naturally found stones made of Aluminium trioxide. Ruby and Sapphire are two important varieties of corundum.

Ruby

It is dark pink or red in colour, sometimes available in brownish or purplish. It is a Cr containing Aluminium trioxide. Its crystal system is trigonal. Its hardness is, next to diamond, 9 in Mohs scale. The refractive index is 1.762 and its melting point is 2050 degree centigrade. It can not be considered as a precious stone alike diamond.

Sapphire

It is also a semi precious stone made of Aluminium trioxide and available in many colours except red. Its crystal system is trigonal and hardness in Moh scale is 9 and refractive index is 1.762. Its melting point is around 2,000 degree centigrade.

These are beryllium containing Aluminium silicate compounds. These are classified to semi precious stones. Available in green, red, yellow and pink. Emerald, Aquamarine, Bixbite and Morganite are some of Beryl stones.

Emerald

This is a variety of mineral beryl. This is green in colour and have hardness of 7.5 - 8. There are some traces of chromium in this compund. Its crystal system is hexagonal and refractive index is 1.576 - 1.582

Acquamarine

This is also one of the Beryllium containing Aluminium silicates and having delicate blue color. Its crystal system is hexagonal and has hardness of 7.5 - 8. Its refractive index ranges from 1.57 - 1.58. It has wide range uses in jewelry industries.

Bixbite

This is a red variety of Beryl. Available in orange red to purple red. Crystal system is hexagonal and hardness in Mohs scale is 7.5 - 8. Its refractive index is1.567 - 1.580 and has melting point around 2000 degree centigrade. Manganese presents in it gives red color to it.

Morganite

This is a light pink colored Beryllium containing Aluminium silicate compound. Its crystal system is hexagonal and hardness varies as 7.5 - 8. Its refractive index is 1.57 - 1.58. Right side shown is one of the larger morganite retrieved from Elizabeth mine in Pala, California in the year 2005

These are skeletal remains of marine organisms(Anthozoa) and have blood like red color. Main chemical content is CaCo3 and it is considered as a semi precious gem. These are widely used in jewelry. Largely found in Great Barrier Reef off coast of Queen island and Australia.

It is a pale white colored hard object produced with in soft tissues of a living shell mollusk. CaCo3 is the main chemical content. The good quality of pearl is valued as gem stone. It is naturally available in the seas. However cultured pearls are more valuable than natural ones. pearls are widely used in jewelry and medicines.