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 Moh's 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.