The measure of relative hardness, Moh's Scale defines common stones and minerals for the hardness and durability. Hardness is one measure of the strength of the mineral relative to its chemical bonds. It is not the same as brittleness, which is related to the structure of the mineral. Hardness is tested by scratching. The higher the number, the harder the mineral. talc (used to write on chalkboards) is defined as the softest mineral and is given the value of 1. Diamonds are the hardest and are given the value of 10.
Moh's Scale is as follows:

1. Talc
2. Gypsum
3. Calcite
4. Fluorite
5. Apatite
window glass or a typical knife blade
6. Orthoclase
7. Quartz (amethysts and citrine)
8. Topaz
9. Corundum (rubies and sapphires)
10. Diamond


The specific gravity is the ration of the density of an object when compared to water. In the simplest testing, it is simply the weight of a mineral compared to its volume. The volume of the stone is measured by the amount of water in displaces.