**How to Identificate gemstone**

**Gems Hardness** is the resistance a gem mineral offers to scratching or abrasion. Thus it’s important property for durability. In 1824, the Austrian mineralogist Mohs selected 10 relatively common minerals and arranged them in order of increasing hardnesses from 1 to 10 as follows:

**Mohs Scale of Hardness**

1. Talc

2. Gypsum

3. Calcite

4. Fluorite

5. Apatite

6. Orthoclase

7. Quartz

8. Topaz

9. Corundum (Ruby & Sapphire)

10. Diamond

**Specific Gravity (S.G.)** is a number expressing the ratio between the weight of an equal volume of water at 4°c. The specific gravity of a gemstone is easily determined and can be an important characterizing property. To determine specific gravity, first weighed the gems fon in air and then in water. The difference in the two reading is the weight of the equal volume of water. Specific gravity can be expressed as follows :

weight in air

S.G. = ——–———————————

weight in air – weight in water

For example, ruby weight 5.00 carats in air and 3.75 carats in water. The specific gravity is calculated as.

5.00

S.G. = ——–————— = 4

5.00-3.75

**Refractive Index (RI)** We can measure refractive of gemstone by use the refractometer.

Refractometer and Contact Liquid,

Important Instrument to identify gemstones.

Ref: http://www.swdgems.com/gem_identificate.html