Precious Opals come in three forms:
Black opal is the most rare and expensive. Some black opals have a full range of color, while others show green and blue hues. These colors are portrayed on a black, or dark colored, body. Next comes Semi Black and Black Crystal. Semi black shows colors on a grey background, the colors are also some what mottled. Black crystal opals show no black potch on the underside of the opal.
Boulder opal is the second form of precious opal. It can be found in many colors and forms. It forms in the cracks and fissures of ironstone boulders and can be cut to standard shapes, but is usually seen cut in free form shapes, as that shows off its enhanced beauty.
Light opal, the 3rd form of precious opal, is much more commonly seen. Many specimens hail from Australia. Light opals display a full range of colors on a white or light blue background. Light opal is translucent and shows the colors well below the surface.
Common opal is less likely to show the flash of color that precious opal displays. Common opal can be found in pink, honey, wax, and green.
Opal's metaphysical properties are vast. Many call it the stone of beauty. It can be worn to bring out inner beauty. It is also looked at as a stone for developing psychic abilities. Some use fire opals, carried in a pouch, to draw money to them. Black opals are considered especially helpful in that they are said to increase the amount of energy used and released from a person during a ritual. It is said that opals contain the colors and qualities of other stones, and as such, may be charged with just about every type of energy possible, making it a very popular stone indeed.