Gemstones are minerals. Out of a total of more than 2000 different minerals, only about 60 odd are commonly used as gemstones. Other minerals are unsuitable as gems because they are too soft and get scratched easily.
A mineral (or occasionally an organic mineral) to be called a gemstone, it must be beautiful in its appearance and color. A gemstone has to be durable i. e. it should be hard enough to survive constant use and handling without getting scratched or damaged. Finally, it must be rare, because its scarcity makes it valuable.
Most of the gemstones are natural inorganic minerals with a fixed chemical composition and a regular internal crystal structure. A few gems like Pearl and Amber come from plants and animals and are known as organic gems.
Then there are some gems, which are synthetic. They do not have natural origin but are made in laboratories. They have very similar physical properties as the natural gems, and can be cut and polished to imitate the real thing. Sometimes these are used as a substitute in jewellery as they cost substantially less than the real gems.
Buy natural Navratan set : 8 gems and 1 american diamond = 9 gems set (without pendant)
Science of gemology: : Gems are scientifically fascinating too. Gemologists make a complete study of each stone, both as it is found in the rocks and after it has been cut and polished. That is why during the formal study of gemology, both aspects are given due importance. This makes them able to distinguish between two similar looking stones, one of which may be fake. The science of gemology looks at these minerals by way of their crystal structure and the physical properties. Everybody interested in buying gems (for whatever purpose) should have an idea of these properties.
Hardness : One of the key qualities of a gemstone is hardness. This means how well a gemstone resists scratching. Higher the hardness, more durable is the stone. Diamond is the hardest gemstone known and has been assigned hardness of 10 on Mohs scale of hardness. The Talc has been given lowest hardness of 1 on this scale. All gemstones are rated in between 1 to 10.
Specific Gravity: This property shows the density of the gem. In common parlance it shows the weightiness of the gem. The greater the specific gravity, the heavier the gem will feel.
Crystal shapes: This can give a definite clue about the gem's internal structure and is used by experts to differentiate between fakes and original gems.
Optical Properties: Researchers and experts to differentiate and decide about the ways of cutting and polishing the gems also use these properties.
Buy natural Navratan set : 8 gems and 1 American diamond = 9 gems set (without pendant)