Opal

Opal is famed for its ability to diffract light. The exact cause of opal's unique properties was only recently discovered by Australian scientists in the 1960s after analysis with electron microscopes. It was discovered that small spheres of silica gel caused interference, refraction and diffraction of light, resulting in opal's distinctive play of color. The varying refractive indices of the spheres and spaces between them dissect the light on its passage through the stone. As light enters the opal, it bends around the tiny particles or 'spheres' of hydrated silica, as well as 'chips' of silicon and oxygen suspended within the stone. Light is comprised of all visible colors and can produce an entire spectrum of colors when it is diffracted.

The following lists some of the most well-known opal trade names, with a short description:

Agate opal - agate with light and dark opal layers.

Angel skin opal - misleading name for palygorskite, an opaque, whitish to pink-colored silicate mineral.

Black crystal opal - transparent to semi-transparent opal, with a dark body color and play of color.

Black opal - precious opal with near-black to black body color. The rarest and most valuable of all opal.

Boulder opal - a thin seam of precious opal on ironstone matrix. Since this is a natural occurrence, its value is higher than that of a man made doublet. The ironstone is very dark, which makes the fire stand out and gives a close resemblance to black opal.

Chocolate opal - precious opal with a brown body color. Also one of the rarest and most valuable opals available.

Common opal, also called potch, is opaque, rarely translucent and shows no play of color. A wide variety of trade names are used to identify common opals.

Crystal opal - transparent to semi-transparent, colorless body with play of color.

Fire opal - translucent to transparent, with a yellow, orange or red body color. May or may not have play of color. Also called Mexican opal or sun opal.

Girasol - almost colorless, transparent opal with bluish opalescence.

Harlequin opal - transparent to translucent precious opal with mosaic-like color patterns. Counted among the most desirable opals.

Honey opal - honey-yellow translucent opal.

Hyalite - glass opal or water stone, colorless, water-clear opal with strong sheen.

Hydrophane - a milk opal, which turns turbid due to loss of water. It can become translucent again and have color play through absorption of water.

Jelly opal - bluish-gray precious opal with little play of color.

Moss opal - milk opal with dendrites.

Opal in Matrix - opal in matrix is similar to boulder opal. Precious opal is dispersed in small fragments throughout the matrix rock, rather than in a seam or even layer.

Opal doublets - a thin layer of precious opal glued to a black base.

Opal triplets - a thin layer of precious opal glued to a black base with a transparent cap composed of quartz or other similar material, such as synthetic spinel or sapphire.

Pink opal - pink opal is delicate, but some opal, such as Peruvian opal, form together with chalcedony, which results in a slightly harder and more durable opal.

Porcelain opal - white, opaque milk opal.

Prase opal - apple-green opal.

Precious opal - displays rainbow-like hues that change with the angle of observation, especially in rounded cut forms.

Semi black or gray opal - precious opal with a dark body color.

Wax opal - yellow-brown opal with wax-like luster.

White opal - precious opal with white or very light body color.

Wood opal - yellowish or brownish opal in the form of fossilized wood.

Opal Gemstone Properties

Opal Color & Occurence

Opal can occur in many colors including white, colorless, pale yellow, pale red, gray, brown and black. Diffraction can cause flashes of any color of the rainbow which can be seen in opal's color play. Yellow, blue and green are most common, whereas violet, red and orange are the rarest colors seen through play of color. Opalescence is usually milky blue in color, but it can occur in rarer colors. The saturation of body color, the play of color and the transparency determine an opal's value.

The most important deposits are located in Australia. Around 95 percent of the world's supply of white precious opals are mined "down under". Famous deposits in New South Wales are at Lightning Ridge and White Cliffs, in South Australia at Coober Pedy and Andamooka. Various deposits are also found in Queensland.

Other deposits are found in Brazil, Ethiopia, Guatemala, Honduras, Indonesia, Japan, Mexico, Russia and the United States (Idaho and Nevada).

Healing Power of Opal

For ages people have believed in the healing power of opal. It is reported to be able to solve depression and to help its wearer find true and real love. Opal is also said to stimulate originality and creativity.

Mystical Power in Opal

Opal is porous and because of this, it is quite absorbent. Due to its ability to absorb, it is thought that it can pick up the thoughts and feelings of people and amplify emotions. Opal is a birthstone for those who are born in October.