Single Stone Identification

The odds on finding an uncut diamond, unless one happens to be walking on a patrolled, electrified, mined and guard dog guarded beach in South Africa, are fairly rare (hence, the phrase "blood diamond"). However, uncut diamonds have a number of characteristics that lend ease to their identification.

They normally appear as cloudy, white or slightly colored pebbles with a unique coal, greasy feel to the touch as they are excellent conductors of heat. Natural diamonds can be dipped in water and will not remain "wet". The water does not stick to the surface. These diamonds do, however, stick to common axle grease when passed over them, but most stones will not.

Natural diamonds also occur as crystals and normally have at least one side of the crystal that is flat and appears as a facet. Sometimes more than one side will take on this characteristic.

Positive identification of diamonds or other gems is achieved by a number of more scientific methods. Specific gravity is a good place to start. This concept is very simple. It is based upon the weight of a certain material in relation to the weight in an equal volume of water.

If the material has a specific gravity of four, it will weigh four times as much as with that much water. Specific gravity is usually checked by using weighing scales that allow suspension of the specimen. First it's weighed in air, then it's weighed in water. The weight in water subtracted from the weight in air with the quotient divided into the weight in air. This gives the specific gravity of the material.

Most gem materials have a specific gravity of less than four. If somebody wants an accurate but fairly fast method, he can produce a few heavy liquids and bottle them to suit his needs. There are a number of liquids such as tetrabromo ethane and methylene iodine that will work. The first having a specific rate of 2.95 that can be diluted with kerosene to any gravity one wishes and the second, 3.33. It can be diluted with toluene to produce a series of liquids of certain gravities in between. Leaving the material in question in the bottle, you can tell at a glance if correct and what the specific gravity and the density is.

The specific gravity of diamonds varies slightly depending on where the diamond came from but will fall between 3.50 and 3.53.