Diamonds are precious, lustrous gemstones made of highly-compressed carbon. Diamonds are one of the hardest materials known.Diamonds have a hardness of 10, a specific gravity of 3.5, and a refractive index of 2.417 - 2.419. Colors of diamonds range from Colorless, yellow, orange, brown, to almost black. Rarer colors are red, blue, green, and purple; these colors (called fancies) are quite valuable. Canary diamonds have a deep yellow color.

A diamond's value is based on the "4 C's": Color, Cut, Clarity, and Carat weight.


Gold is a precious metal that has been valued by people since ancient times. People use gold for coins, jewelry, ornaments, and many industrial purposes. Until recently, gold reserves formed the basis of world monetary systems.

Gold is a very soft metal when it is pure (24 Kt. is pure gold). Gold is the most malleable (hammerable) and ductile (able to be made into wire) metal. Gold is usually alloyed (mixed with other metals, often silver and copper) to make it less expensive and harder. The scientific abbreviation of gold is Au.

The purity of gold jewelry is measured in karats. Some countries hallmark gold with a three-digit number that indicates the parts per thousand of gold. In this system, "750" means 750/1000 gold (equal to 18K); "500" means 500/1000 gold (equal to 12K).

Karat Percent Gold
24 Kt. 100% Gold
22 Kt 91.6 % Gold
18 Kt. 75% Gold
14 Kt. 58.3% Gold
10 Kt. 41.7%


Silver is a fine, silver-white metal often used in jewelry. Pure silver has a hardness of 2.5. Other metals are alloyed with silver (usually copper) for silver used in jewelry making.

Silver tarnishes after exposure to air (a thin layer of silver-oxide forms on the surface). Silver often occurs near copper lodes.