Alternative Identification Methods

Another reliable indicator used is a scale of hardness indicator. As most people realize, diamonds are the hardest stone in the world. The hardness scale normally refers to something called Mohs hardness.

The Mohs scale is a 0 - 10 scale. There is another scale that's 0 -15 making it easier to differentiate between the marginal gems that fall between 9 - 10, but the Mohs scale is primarily in use. Hardness simply refers to the ability of one material to scratch another. Harder material always scratches a softer material. The difficulty in making the scratch or appearance does not come into play. Simply the fact that it can be made.

It should be pointed out that the Mohs scale does not correlate to the relative hardness of the materials. In other words, a diamond is not something that is 10x harder than something that is a 1 on the scale. The scale is simply there to present a basis on which, when a material is scratched, another material can be identified as harder.

Diamonds are a 10 on the hardness scale. Quartz is a 7 on the hardness scale as are most types of tourmaline. Most garnets are 7 1/4 on the scale. Synthetic emerald tends to be 7 1/4 to 7 1/2. Silicon carbide is a 9 1/4 to 9 1/2 on the scale, meaning it will not scratch diamond and diamond will scratch it. Opals begin at 4 1/2 and go up through 5 on the scale while turquoise is 5. Rubies are 9 on the hardness scale.

It is also possible to set a piece of gem material between two Polaroid plates that are set so that no light may be seen between them. The lower plate that the gem sits on is known as a polarizer. The upper plate is the analyzer. The polarizer is fixed but the analyzer is rotated.

If during a complete rotation, the material remains dark with no change, it is called isotropic. If it is non isotropic, it will change from light to dark four times during a complete rotation. The normal non isotropic pattern is a sharp cutoff from light to dark, much as extinguishing a fire. By doing this with a gem, it is possible to establish a refractive index. However, this is a fairly mind boggling exercise and there are easier ways to tell, at least with diamonds.