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Astrology Birthstones Main page Trip to Paris | What is Opal? Although opals come from all parts of the earth, black opal comes from only one place on earth - Lightning Ridge, Australia. When travelling to Australia to talk with our opal suppliers, we gather together only the finest quality opal to sell to you! Opals are one of the most beautiful and sought-after multicoloured gemstones in the world, because of all the known precious stones only an opal can show the complete range of spectral hues in glorious balance. The special characteristic of these gems is their opalescence (duh! -D), a rainbow like iridescence which (especially in rounded forms called cabochons) changes with the angle of observation. Using a scanning electron microscope with a magnification of 20,000x reveals the cause: microscopic spheres of the mineral crstobalite layered in siliceous jelly cause the reflections, or interference patterns. Opal is the birthstone for people born in October. During the late 1800's and early 1900's, was believed to bring bad luck for the wearer. Now we know better! Most minerologists will tell you that the word opal is derived from the Sanskrit upala, meaning 'a precious stone'. Opal is a noncrystalline form of the mineral silica which, despite its amorphous structure, displays an amazing degree of internal organization. Opal is related to its more commonly found but highly crystalline cousins quartz and agate, and is formed from amorphous "balls" or lumps" of silica rather that from ordered, naturally faceted crystals. The chemical composition of opal is SiO2H2O, silicon dioxide combined with water (an opal stone may contain up to 30% water.) The silicate minerals in the stone add to its weight, giving it a specific gravity ranging from 1.98 to 2.5 times that of pure water. Opal's scratch hardness is measured at 6.0 to 6.5 on the Mohs' scale, similar in hardness to quartz, a little more than halfway between the hardness of talc and diamond. Most opal is more than 60 million years old and generally dates back to the Cretaceous period when dinosaurs roamed the earth. It is found near the earth's surface in areas where ancient geothermal hot springs once flowed. The minerals bubbled up from beneath the surface of the earth and slowly, over the centuries, lined the walls of cracks, vents and underground cavities in the bedrock. Most opal is found where geothermal hot springs dried up during seasonal periods of rainfall and extended dry periods. Mors than 90% of the world's quality gem opals come from Southern Australia, although it can be found in other parts of the world such as Brazil, Mexico, Czechoslovakia and Nevada. All black opals (see below) come exclusively from Australia. The story of opal inn Australia begins more than million years ago when the deserts of central Australia were a great inland sea, with silica-laden sediment deposited around its shoreline. After the sea receded and disappeared to become the great Artesian basin, weathering 30 million years ago released a lot of the silica into a solution which filled cracks in the rocks, layers in clay, and even some fossils. Some of the silica became precious opal. Opal is one of the few gemstones that is sedimentary in origin. The water in opal is a remnant of that ancient sea. The most striking quality of opal is its ability to refract and reflect specific wavelengths of light. In fact, the term "opalescence" was coined to describe this phenomenon. The size and spacing of the amorphous spheres of silica within the stone refracts specific wavelengths of light; each sphere refracting a single, pure spectral color much like the individual microscopic droplets of water in a rainbow. The interplay of these pure wavelengths of light gives opal its unique visual appeal, and makes it one of the most sought-after gemstones in the world. Opal was introduced into Greece during the first century B.C. The Greeks called it opallios, a word coined from two other words, the first of which gives us words such as opaque and optical, while the other gives us words like alias and alter. Thus, opal really means 'to see a change of color. Some people think the opal is bad luck when worn if it is not your birthstone. This is not true. The story was started by Sir Walter Scott in his novel Anne of Gierstein, in which the heroine of the novel has her life force caught in the beautiful opal she wears and she dies when the fire in the opal is extinguished. In ancient times opal was accepted as a symbol of faithfulness and confidence. The name "opal;" is derived from the Latin word opalus, meaning seeing jewel. The Arabs believed that opals fell from heaven in flashes of lightning, and that's how they received their fiery color. Opals are very powerful in ritual magic. Since a quality opal contains every color of every other birthstone, it can be used or charged with all the energies and powers of the other stones combined and can be used in place of any birthstone for spells, rituals or other magical needs. Opals have been linked to invisibility and astral projection. and have been used to recall past lives (each color supposedly represents a past life). It has reputed healing properties, especially to increase mental capacities such as creative imagination and other unused powers of the mind. Opal is a "living" stone, which means it must be protected from heat and detergents that "dry" the gem. Opals develop crazing if they are allowed to dry out. Heat treatment is catastrophic!! In addition to cracking, loss of water causes loss of iridescence.
Care must be taken when polishing and setting opals. Despite their hardness, they are prone to crazing and cracking, and loss of water content causes a noticeable loss of iridescence. To prevent this, opals are normally stored in moist cotton wool or cloth until it is time to work with them. Sometimes, an opal that has lost its opalescence may be "rejuvenated" by rehydrating the stone with water or special oils, but this may only temporarily improve the stone's appearance. In the opal cutting process the potch (a kind of mineral crust) is ground away from the presentation areas of the gem opal. This process unlike diamond mining, where the blueground (Kimberlite) is crushed away from the diamond crystals. Individual opals are "dopped" -affixed to the ends of wooden dowels about the size of old fashioned wooden clothespins, usually with dopping wax, which resembles sealing wax. Grinding and polishing of opals is done under a cold water drip to prevent the stones from overheating and cracking. A series of grits is used, from coarsest to finest, to produce the desired finely polished surface that reveals the full play of color in the opal. Most gem opals are ground to a highly polished convex oval shape called a "cabochon."
Wear it often it likes to breathe. Touch it often. It likes contact with the skin. the natural oils in your skin keeps the opal "moist" and lustrous. (Contrary to popular belief, true Australian opal is not porous and will not absorb contamination in perspiration or other bodily moisture.) Do not wash dishes, clothes or other items with it on. Opals contain water. The harsh detergents in dish or laundry soaps can "dry" out the stone. Do not garden with it on. continuous contact with the soil can abrade the surface of your stone. Do not clean your opal jewelry with ultrasonic device. Use plain water and a good, nonabrasive had or facial soap. Do Not store your opal in oil or glycerin. Gem Opal Precious opal, which displays "opalescence" (spectral color, iridescence that changes with the angle at which the gem is viewed), is the kind of opal with which most people are familiar. White Opal is an opaque stone in which the colors appear as flashes or speckles.The white opal, when used in rituals on the full moon night, is said to bring the moon goddesses' powers to full fruition in the practitioner. Black Opal - Precious opal with dark gray, dark blue, dark green, and gray-black basic colour, or potch. Deep black is an exception. Black opal contains fire with a dark body color. These are less common and tend to be costly. These are the investment high quality opals !Black opals are much rarer than white opals.Black opals worn near the heart on necklaces made of gold are said to ward off evil, protect one from the evil eye and protect travelers on journeys to far away lands. Opals have been ground up and used a magic potions to heal the body, ward off bad dreams, and used an energy enhancement tools.Black opals are the tools of choice for witches and magicians, who use them primarily to enhance their magical receptive or projection powers. Opal Matrix - Banded growth or leafed inclusion or precious opal with and/or in the matrix rock. Boulder Opal - Precious opal with a dark base surface, colour play, and a high density. Occurs as pebble rock, where opal fills the hollows. Harlequin Opal - Transparent to transluscent precious opal with effective segmentation of colour patterns. Counted as among the most desirable opals types. Crystal Opal - A few red reflexes on colourless, vitreous surface.Crystal opal, the next most costly type of opal, is transparent with flashes of color. It is highly valued for the brilliance of its colors and the fact that many layers of color can be seen within the stone. Girasol - Almost colourless, transparent precious opal with a blueish lustre. Opalized organic material may consist of wood, plant stem, bone or shell that has been petrified under extremely rare conditions. Boulder Opal another unusual type of opal is boulder opal, which has opal with an ironstone host rock matrix which creates a natural dark background to view its fire. These sometimes occur in "splits," a matched pair of opals created when a price of boulder opal is split along the opal vein. These are particularly favored for earrings, since they are mirror images of each other. Fire opal is transparent or translucent with an orange or red body color. Fire opals are named for their reddish color but are opalescent. Be careful not to misinterpret the term "fire" as iridescence, because in precious opal (with a play of iridescent color) the play itself is also called fire. Much of the world's fire opal is mined in Mexico.Fire opals are often used in money rituals to draw funds to those who are in need, normally worn as a pendant on a gold necklace, one surrounded with 10 or 12 small diamonds. Common Opal is rather opaque with no spectral play of color. Many names are used to describe common varieties. Among these are honey opal, milk opal, and moss opal. Examples include milky agates and certain "petrified" opals.
Evaluating opal quality is a specialized business. It is difficult for the average person to tell the difference between a moderately valuable stone suitable for a ring or a pendant and an investment grade black opal worth as much as $20,000 per carat. In addition, the buyer must beware of the relatively recent appearance of "created" or synthetic opals, and of "manufactured" opals that consist of thin layers of true opal material bonded together to make a more substantial gem. some unscrupulous gem sellers have even gone so far as to grind inferior opal material and mix it into a clear epoxy resin, which is then cast into the traditional cabochon shape. With these caveats in mind, in general, when you see a stone you like, buy it. some factors you con consider in evaluating its quality are the play of color, its "fire," "sparkle" or intensity, the rarity of the color or colors, and how "directional" the colors are. Intensity The finest gem opals look like someone has turned the color knob all the way to the right. There's nothing subtle about them. They flash and flare and seem to glow with a mysterious inner fire, even in indirect light. One way to spot the most intense stones in a tray of opals is to squint at them and see which ones "pop" out from the rest. (An aside: one of the worst ways to view them is in the harsh halogen lightning of your typical "mall" jewelry store.) Color Color in opals ranges from the finest milky white to a beguiling azure-green to the rarest and most expensive opal of all, a deep, red-flecked black. Red in any opal is an indication of quality, and therefore greater worth. the iridescent red flecks in most gem-quality opal is also an indication of "fire" or "pinfire," a common measure of an opal's worth. For those who are interested in a pleasing piece of jewelry rather than investment, color preference is a matter of personal choice. In that light no single color is better than another. Direction An opal has a definite "direction." The finest opals will show a bright play of color across the entire stone no matter how the stone is viewed. Others may display their colors only when viewed from certain angles. Still others may display their colors from a single viewing angle. In general, the narrower the directional the play of color, the less valuable the opal. The presence of potch - opal that has no play of color, usually white, gray or brownish - on the surface of the opal reduces its value for the same reason, lack of appearance of direction. Opal Doublets and Triplets If you are on a limited budget, consider an opal doublet, which is an assembled stone with opal on top and another stone, usually obsidian or ironstone, laminated to the back. These are produced to take advantage of high quality opal material that is too thin to stand on its own. Because there is less gem opal involved, they cost a lot less, and the dark background really shows off the play of color in the opal. A high quality doublet will give you the look and beauty of a fine black opal at a fraction of the cost. Avoid the opal triplet, however. These are assembled out of three materials; the dark background (usually obsidian), a whisper of opal, and a lens-like quartz cap on top. Triplets are cheap, but they tend to look it - and they can fog up when humidity gets between the opal and the quartz cap. Once this happens, they're ruined. Synthetic Opals Several manufacturers make synthetic opals, including Gilson Opal, Inamori Opal, and others. In general, synthetic opals look too good to be true, with exaggerated fire and iridescence, and a consistency from stone to stone that nature could never duplicate. I have seen tennis bracelets costing upwards of $1,000 made entirely from synthetic opal, and every stone looks exactly like its neighbor. Quite good, in fact, but by their very consistency they betray their synthetic origin. this may be for you, but nature is quite a bit more canny than the most sophisticated laboratory man can devise no two natural opals - unless cut from the same stone - will look the same. Opal Enhancements Opals can be enhanced by treating them with certain substances and processes. They may be impregnated with plastic or epoxy, surface oiled, soaked in sugar-rich solutions in a sulfuric acid bath to bring out a peppery pinfire effect, or heated in paper or manure to leave a deposit of carbon below the surface. All of these enhancements are temporary, and will not increase the value of the original stone. some of them lead to detrimental effects such as low specific gravity, high porosity, and increased brittleness. Beware anyone who admits to treating stones in these ways, as they are misleading and ultimately damaging to the stone.
Rough opal parcels are sorted into three grades: tops, middle, and low. Each tops parcel has a King stone, which is the best stone in the parcel. Some parcels have several King stones. Colour is the primary criteria for grading, but the graders also take into consideration the number of imperfections and faults, and whether a stone is the right shape to be cut into an oval or one of the other popular shapes.You can buy rough opal in several different conditions. Mine Run. Direct from the mine. The stones have not been cut or ground down. This means that there is more guess work in the cutting. Purchasing mine run opal can be risky if you are not very experienced. Off Cuts. The miner has removed whatever opal he has a market for and sells you what's left. With off cuts, you can usually tell what you are going to be able to cut. You must still watch for cracks in the opal because once a crack becomes obvious, a stone can lose half its value. Rubs. This can often be the best way of buying rough if you are not very experienced. The miner has cut and ground the stones into basic shapes, after having removed most of the rubbish. What you have left is the stone nearly ready for the dopping and polishing process. You have the satisfaction of cutting your own stones without the high risk of buying mine run rough. Opal is officially sold in troy oz. there are 20 d.w.t pennyweights to a troy oz. There are approximately 30 grams to a troy oz and approximately 30 oz to a kilo. Here's an ecclectic assortment of hints and tips you may find helpful when buying or working with opal. 1. Not all opal is valuable. Potch, sometimes called "common opal" does not reflect colours. Potch does have its use, however, as a backing for doublets and triplets. When there is color mixed with potch it's called "potch and color." 2. Some classes of rough opal are unsuitable for making gemstones. Some are very porous. Others have a chalky appearance. Still others can lose their colour in a short period of time. And yes, it is common for certain types of opals to shatter in a dry atmosphere when the water from the gel evaporates. The best protection for buyers is to purchase opal from a knowledgable and reputable dealer who accurately details exactly what you are purchasing and is willing to guarantee the stones. Note: If you buy rough opal, there is no guarantee that it will not crack. This is the calculated risk you take and is part of the "excitement" of opal cutting. 3. When examining opal jewelry, look at the stone from the side to determine whether it's a triplet. Solid and doublet opal domes are simply the opal formed into a curved dome shape. Triplets have clear crystal domes to protect the flat opal surface. 4. It is very difficult to tell whether a stone is a doublet or a solid if it is in a setting. It helps if the back of the setting is open, but it is still no real indication because the back of a doublet and a solid looks very similar, although a doublet is usually perfectly black on the back whereas a solid black opal usually has some imperfections. So if the back of a stone looks too perfect, you have to be a little suspicious. For this reason it's best to buy opal from reputable dealers who know what they are doing because, unfortunately, many jewelers also are not experienced in opal. 5. When buying opal over the net, ask the seller to give you a summary of how close the graphic sample is to the real thing. Opal is very difficult to photograph and the appearance on the computer screen may give it a different look. Particularly is this the case in regards to size. Graphics come out in all different sizes, usually a lot larger than actual...so make sure you get your ruler out and actually draw the size on a piece of paper so that you will know in your own mind's eye the actual size of the stone. 6. The same thing applies to the colour of the stone. Make sure you get the supplier to give a commentory on the colour so that you will know pretty well what you are getting. The camera sometimes picks up colours that are only minimal, while ignoring the feature colours.
Opal Lore
The Aztecs mined opal in South and Central America. Opal was also treasured in the Middle Ages and was called ophthalmios, or "eye stone," due to a widespread belief that it was beneficial to eyesight. Blonde women wore opal necklaces to protect their hair from losing its color. A beautiful opal called the orphanus was set in the crown of the Holy Roman Emperor. It was described "as though pure white snow flashed and sparked with the color of bright ruddy wine, and was overcome by this radiance." Opals are also set in the crown jewels of France. Napoleon gave Josephine a beautiful opal with brilliant red flashed called "The burning of Troy," Do you like my page? Did you find something interesting here? Could you please sign my guest book or send me e-mail? |
