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Opal
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Opal
Opal

 

Opals are a unique category in that they are very different from all other gem-types

They have a long history of symbolic meaning dating as far back as ancient times, when they were considered to be emblems of fidelity and safe-guarding. They were even believed to have therapeutic qualities in cases of eye diseases and memory enhancement. Today they are prized for the unique rainbow effect they have, and the sheer multitude of variations that can be seen. Opal is composed of hydrated silica spheres formed within ironstone. These silica spheres reflect light at different angles and color each ray with slightly different color. This is how the rainbow affect is achieved and in opals, the brighter and more colorful the rainbows within the stone- the better the opal.

Opals are evaluated with this rainbow quality in mind; purity and intensity of color, flawlessness and brilliance are the main deciding factors in this gem. When the term ‘body-color' is used in reference to opal this indicate the darkness or lightness of the background color. Generally, the darker the body-color, the more valuable the stone. The brilliance of the gem is estimated like in other gems, and those that display bright colors in all kinds of light are the most highly priced. The ‘play of color' refers to the combination of colors at play in the gem and the rarity of these colors. Generally, the more red ‘dots' on the gem, the more it will cost, as red silica flecks are very rare. Blue and green flecks are more common and they should slightly less than the red.

This is a fairly soft gem, rating only a 5.5 on the Moh scale, so it should be worn with care. Wearing an opal in bright sunlight or leaving in a hot place is never recommended, as they are sensitive to temperature changes. Opals are found either very clear with the flecks plainly showing, or murkier with dark color. The murky ones are called ‘water' opals or ‘Jelly opals'. Jelly opals are sold by size, but we will price them here in approximate carat weights. Gems less than 15 carats of good quality will sell for about $35-$80, better, ‘fine' grade quality will sell for $80-$250 and extra-fine grade will sell for $260-$770. They are cut only in the cabochon style because faceting such a gem would only decrease its value. Higher domed cabochons display the stone better and cost more than flat-domed cuts. Usually they are oval-shaped, as this has ever been the traditional cut for the stone, but today you can see more and more irregular shapes that give an interesting new twist to the presentation of the gem. The smoother and more polished an opal is, the more light will reflect off it and dazzle the eye. Any imperfections reduce price significantly, especially the common opal flaw called ‘crazing', which is a thin network of fractures on the surface of the gem that looks like a spider web.

The rarest and most expensive kind of opal is called ‘harlequin opal' and it displays a checkerboard effect of dark and light spots. There is absolutely no chance you will encounter a gem of this type in the market. The most prized of opals that are available are the Australian ‘black' opals from Lightning Ridge, which are usually dark grey with flashes of color sparkling off them. These are extremely rare and not seen very often in the market, with the opaque stones valued higher than the clearer ones. They cost quite a lot, even relative to the gem-world; - even small stones are being valued these days for $20,000-$30,000. Be very wary of anyone offering you a black opal, as doublets and triplets in this case are very frequently seen.

The most commonly seen opal in the market is the ‘Light' opal, opal that has some play of color. It is typically off-white in the background of the stone with tiny flashes of white light that reflect off it. If it is opaque and lacking in luster it will retail for relatively little, but very fine, translucent white opal can cost from to $200-$300 per carat weight and if it's entirely transparent it may be called ‘crystal opal' and cost up to $2500 per carat.

‘ Boulder opal' refers to opal that is still attached to the rock in which it was found and resembles either light or dark opal. It is found in Queensland , Australia . They are sold by size and not carat-weight. These are lovely pieces and very popular around the world. They are usually cut in irregular shapes to accent the ‘earthy' quality of the gem and may sell from a few hundred dollars for a medium sized stone and up to $40,000 and $50,000 for a good-sized, fine-quality grade. The usual price range for boulder opals when measured in approximate carat weights is quite complicated. Small pieces of less than 5 carats may cost, on average, between $85 to $2500 for good quality stones, $2800 to $6500 for fine quality and $6700-$14,000 for extra-fine quality. Medium-sized pieces (of about 5 to 10 approximate carat weights) will cost about $1000 to $2800 for good quality, $2900 to $12,100 for fine quality pieces and $12,150 to $22,100 for very fine pieces that display great body color and sparkle. The large boulders (approximately 10 to 30 carat weight) may cost from $1220 to $6500 for good quality, $5700 to $23,200 for fine quality and finally $16,200 to $75,000 for extra-fine quality stones.

‘Matrix' opal is also an Australian product; it's a piece of rock that has opal lines running through it and they mined in various sized chunks from the bare rock. The less expensive kind in mined in Andamooka , Australia and the finer grade matrix if found in Queensland . It should sell for much less than any real pieces of opal, and many people buy them as decorations for the house. ‘Fire' opals are found mostly in Mexico and they mainly translucent with brown, orange and yellow body-color. Some display the classic play of color while some do not. The most expensive kind is the reddish, orange variety that sparkles brilliantly with color and they can sell for as much as $300 per carat. For ‘fire' opals, as with ‘light' opals, the higher the transparency, the more valuable the stone. As with most of the gems in this list, opal is also misrepresented with false names. “Japanese opal' is a misnomer for a plastic imitation circulating the market, “Gilson opal” is actually a synthetic imitation and “Slocum opal” is also an imitation, made from various materials.

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