Opal Gem

Jewelry Trends Jewelry Metals Gemstones

Fashion Beauty Celebrities

Modeling Only for men Only for women

Opal is the most famous and precious of the silica gems, owes its renown to the vivid flashes of colored light that the stone reflects. These flashes can be evenly spread over a large part of the stone's surface or they can come from numerous irregular patches or points of light which cover it with radiance made up of all the colors of the rainbow. No other precious stone can show such bright and pure colors.

The 'play of color' in opal is produced by quite different means from that which colors other gemstones: its produced by the diffraction of light, not by its absorption. This is an effect similar to that which gives the bright metallic colors to the plumage of humming birds, for instance, but clearer and stronger, because the active principle in opal is even more delicate. It consist of an array of ultra-microscopic spherules forming layers within the stone and acting as a three-dimensional diffraction grating of the utmost fineness.

This difference in internal structure is the essential feature that distinguishes precious opal from common opal (amorphous silica), of which there are many varieties. Perhaps the best known of these is the fossil wood of petrified forests, where silica has replaced the fibres in ancient trees so exactly that their structure can still be seen in every detail. Another variety is cachalong, which is white and resembles porcelain; it is so porous that it will adhere to the tongue. Common opal is usually translucent and can occur in many colors. Precious opal is classified by its body color into four groups: black, white, fire and water opal.

Black opal, in which the jet black background sets off the play of color to perfection, is the rarest and most valuable variety. Only a small proportion of gem material, all from Australia, is truly black.

White opal shows its colors against against a milky or greyish background. This is variety that has been known and prized since ancient times.

Fire opal is so named for its transparent or translucent orange to red color, not necessarily for any fiery glints. Much of it shows no least costly of the gem opals and is often faceted while all other opals are cut with a flat or domed top.

Water opal is completely colorless and transparent, which gives the play of color within it a curiously quality.Opal matrix consists of specks of veins of precious opal contained in dark brown, opaque limonite from which it is not worth separating the opal.

Precious opal frequently fills quite thin fissures and is therefore often cut into thin flat stones. Sometimes these are so thin that they would soon break in wear and therefore cemented to thicker pieces of common opal, onyx, or even black glass. These opal doublets are usually sold for what they are and the joint between their components is often visible. When it is hidden in a setting it may be very difficult to determine the true character of the stone without unsetting it.

The stupid superstition that it is unlucky to wear opals dies hard but it has not depressed the value of stones of good quality. Until quite recently it has been impossible to imitate at all convincingly, but recent reports from Australia state that a synthesis has been successful and that commercial exploration is feasible.

Shop for Opal