Sapphire is the common name for transparent corundum. Its mineralogical name is aluminum oxide. Albeit the usual color of sapphire is blue, it also comes in just about any other color as well. Brilliant orange sapphires are sometimes called padparascha. Red and most pink corundum is called ruby, while blue corundum is called sapphire. Sapphires cover the spectrum, and are available in a rainbow of colors . . . colorless, red, pink, blue, black, brown, orange, yellow, green, indigo, violet, and mauve. The different colors are a result of mineral impurities, usually metallic oxides. This is a case in which impurities are a positive thing. Impurities of chromic oxide create bright red coloring that give us rubies. Impurities of ferric oxide create a yellow color, while titanium oxide produces bright blue.
As to what color of sapphire is the dearest and "best," many people believe that "the darker, the better," and that is not necessarily true. The most desirable sapphires are ones which have intensity of color and sparkle, which in large measure are a result of skillful cutting of the stones. The bottom line, as always, is that "the best" is whatever the individual finds most appealing.
Corundum is very hard, a 9 on Moh's scale. Diamonds measure a ten. Because of its hardness,
corundum is often used as watch bearings, watch glasses, and as an abrasive. The best sapphires and rubies came from Burma. There, we believe, they had been mined as far back as prehistoric times. Documentation tells us that they were definitely mined when Marco Polo was alive.
Kashmir is another source of fine sapphires. The area is known for cornflower blue stones.
Thailand is another source for sapphire. The term Ceylon sapphire is used in describing sapphires in pale to medium. If a sapphire comes from Sri Lanka it is known as "Ceylon-type" sapphire. Today, we find sapphire mines (particularly dark colored stones) in Australia and we call "Australian sapphire" those that are dark in color, whereas the "Ceylon sapphire" denotes lighter stones. Sapphires can also be found here in the States, in Montana and Colorado, as well as in India. Small amounts are found in several other countries as well.
Sapphire jewelry can be cleaned using hot soapy water, or detergent and rinsed thoroughly. Enzyme cleaners and cleansers containing chlorine should be avoided. A toothbrush makes an excellent tool to clean away dirt and grease.