Opal Gemstone Information

 

Opal is one of the more popular gemstones, mainly due to its wonderful variety of rich and beautiful colors. Opals are known for their majestic fire displayed, almost floating, inside their body. This phenomenon is known as "play of color" or opalescence. Many Opals are recognized by their dark blue and green color with spots of red. White opal on the other hand displays orange-red and greenish-yellow colors. Fiery orange color is seen in Mexican opals.  With an incredible number of forms and colors, every Opal gemstone is unique in its own way.  Precious Opal is found in many different varieties:

Black Opal - It is the most sought after variety of opal. It is treasured all over the world because in this particular body color, the color play is displayed at its best. It comes in all deep and dark color variations. The natural basic black color highlights all the different colors in the best possible way therefore the color play is very impressive in this gemstone. Solid black opal is the most valuable.

Semi-Black Opal - The body color in this stone varies from grey to almost black. It gives more of a smoky look. It is easily available in many areas.

Crystal Opal - It comes in lighter and delicate shades on the top. Many layers of colors are seen in it. All color variations are available in this variety. Light colors make this stone translucent. It comes after black opal in the priority list of pricing.

Boulder Opal - It possess natural brown body color or the back that appears black from the front. It is too available in all color variations. Often it possesses rolling surface and ironstone inclusions. It can be given any innovative cut. It is ideal for earrings.

White Opal - Last but not the least, this variety exhibits scattered colors and is opaque in nature. It is also called as Milky Opal and is very economic to buy.

Harlequin Opal - It is most rare and expensive variety. It comes in irregular tile pattern with black body color. It looks very similar to that of the widely created man made opal known as 'mosaic opal'. Buyers need to be vigilant at the time of purchase of this variety else they might land paying the price of Harlequin opal and take away mosaic opal.

Fire Opal
- The basic color is orange or red, both colors are related to fire thus, this variety is named accordingly. It is mostly procured from Mexico. Fire opal is an opal gemstone in itself and not just an imaginative term used to describe the color play of any other variety of opal.

White Opals These are perhaps the most common. If they have little flash in them, they shouldn't be as expensive. The more flash they have, the more valuable they are. A white opal in a larger size loaded with color (especially reds, pinks and oranges) will command a premium price.

Jelly OpalsThese are sometimes in line with white opals or slightly less pending on the retail price guide you look at. It is like a white opal but instead of flashes of color, it has more of an effect of several zones of color like neon tubes or a plasma effect. If you could imagine a piece of multicolored silicate gel that shifts every color of the rainbow within it, that's what a jelly opal is. The phenomena is more like a color shift property across the spectrum where the colors blend than it is patches of flash like other opals. If you like something that has an antique motif to it, you might like these as they have that effect to them.

Boulder Opals - These come from a certain mine in Australia, and they typically have a greenish blue body. They can command a higher price than a white opal. If it has a lot of violet flash in it along with some yellow and red, those can fetch premium prices. Look at the backing underneath to make sure it's not a doublet. Most of what is in retail jewelry stores now days that appears to be a Boulder opal is in fact a doublet. If you visit a high end retailer, that's another story. The more variety of color within the specimen, the more desirable the piece. Smaller sizes are more common than larger ones. It's more difficult to find a specimen with more flash and more of a variety of color in it. You will pay more for that. Some collectors love these things, and they make some beautiful pieces of jewelry when set in something like a bracelet or pendant. They also make great cuff-links for men and tie-tacks if you wear those.

Crystal Opals  - These tend to be uncommon in the retail market. The price guides have these listed for premium prices. When I say premium, a 1 carat stone of very good quality can go for around $1000/carat. If you want to double the size, triple the price for comparable quality at a retail level. You might find smaller accent sized stones in your better department stores if you're lucky or a higher end jeweler. You may see these in estate pieces such as bracelets. They have a transparent to translucent clear body. Typically you see a lot of flashes of blue and green in them. Certain specimens may have a little bit of a jelly undertone to them here and there, but they are still considered to be crystal opals. T e more flash, the more color, the better the quality. The best ones come from Mintabie, Australia and from Ethiopia. However, the ones from Mintabie are said to be not quite as sensitive to heat in comparison to others. However, treat them with the same care as you would any other opal. These are highly sought after by collectors.

Semi-black Opals  - There is many a dealer who will call a semi-black a black opal when technically it's not correct. However, it is somewhat a generally accepted practice to call a semi-black a black. In the price guides, some will put them on par with crystal opals. Others will put them a little bit higher in price. So what's the difference? It's basically a crystal opal with more tone. When you see a translucent smokey grey body in the piece, that's a semi-black. Technically, if a crystal opal has a tone on the GIA scale between 4 and 6, it is considered to be a semi-black. Those are rare and often put in the same category and class as the famed black opals. You might have an easier time finding a semi-black opal with a lot of color and fire in it in comparison to it's black counterpart.

Mexican Fire Opals - These generally can be described as a jelly opal or in some cases like a regular opal with one difference. It has a transparent or translucent orange body. If you can picture the color of a really good mandarin garnet, or orange jam, that's what the body is of the color. Prices can very from very inexpensive to expensive pending on the amount of flash. They are available in more appreciable sizes, but not necessarily with as much fire to them as other species. However, when they have the fire in them, they can bring premium prices as those are not so common.

Pink Mexican Opals - These are mined out. If you see a true pink opal, it's a true collectors item. You'll only find them in an estate piece. They're like a white opal and they have a more or less opaque body to them, but they have the flash and fire of other opals. They are very rare. They were once popular circa 1950's or thereabouts. There are no more coming out of the ground. They haven't been around for many years, but they are a truly unique specimen. If you happen to find one of quality, and it's within budget, it's a true collectors stone that few can truly appreciate.

The prices, uses and value of Opal vary tremendously, depending on the size and quality of the gemstone. AJS Gems is your source for the highest quality colored stones from across the globe, available at Bangkok direct wholesale prices. Creating the finest jewelry starts with finding the best gemstones, and the best gemstones are found at AJS Gems.

 
Why Buy Loose Gemstones Instead of Pre-Set Jewelry?
 
There are many reasons, but basically it boils down to value and choice...

When buying your opal gemstone loose instead of a pre-set stone, you can be sure you are getting the best value for your money.  Loose gemstones are less expensive, a better value, and you can really see what you are paying for.  The most important part of getting the right price and finding the best value is to first see what you're getting.  A jewelry setting will hide the inclusions inside a gem, and can deepen or brighten its color.  With a loose stone you can much more easily inspect the gem and see it for what it really is.  In this way you can get a better idea of its true worth and be sure you are paying a fair price.

The second advantage of buying a loose gemstone is choice.  You are free to pick the exact color, cut, shape and variety of the stone for the setting of your dreams, be it yellow gold, white gold, platinum or silver; prong set or bezel set with diamond accents.  You can experience the joy of creating your very own, one-of-a-kind jewelry design. Choose from a variety of jewelry settings and styles to create a completely original presentation that will perfectly suit your individual gemstone and will be as unique as you are!

 

 Opal Ring                                                                   Opal Jewelry

 

Attributes

Origin  
Australia, Brazil, the Czech Republic, England, Honduras, Mexico, South Africa, and the United States
Color Black, white, gray, yellow, orange, red, green, blue, colorless.
Refractive Index  1.45
Chemical Composition SiO2·nH2O
Hardness  5.5 - 6.5
Density  1.98-2.50
Crystal Structure Amorphous
Month October
Zodiac Signs Libra, Scorpio and Aries

Opal is considered a mineraloid and has no crystal structure. The term used for no structure is amorphous.  Opal is scientifically written as SiO2 NH2O, hydrated silicon dioxide.  Opal is normal a stone that includes a significant water content. Stones that can commonly form Opal are limestone, basalt, rhyolite and sandstone.  While Opal contains water, the water content does vary by stone.  For instance, Opal has been found with water content approaching 20%, however, most Opal stones used for ornamental jewelry usually have water content of 3% to 10%.

Opal is rated at 5.5 to 6.5 on Moh's Scale of hardness. The physical structure of Opal is unique. Tiny spheres of silicon dioxide form a pyramid shaped grid interspersed with water. Tiny natural faults in this grid cause the characteristic opalescence or "play of color". The effect is similar to the rainbow colors displayed on a soap bubble, only much more dramatic. The incredible play of color is exhibited by the gemstone due to the presence of small spheres in the silica gel that causes interference and refraction appearance. Silicon and oxygen chains are packed in the spheres and these are uneven in size and incoherent in concentration. These are set in a compact structures thus, when ray of light falls it dissects the light on its way through the stone resulting in the awesome color play. As per the size of the spheres within the structure, changeable colors of the gamut are diffracted. With the increase in the consistency of the spheres position, more intense and brilliant would be the color play.

Opal has a refractive index of 1.45 and a vitreous to resinous surface luster.  The refractive index (RI), measured using a refractometer, is an indication of the amount light rays are bent by a mineral.  Birefringence is the difference between the minimum and maximum RI. When birefringence is high, light rays reflect off different parts of the back of a stone causing an apparent doubling of the back facets when viewed through the front facet. 

Most gems have a crystalline structure. Crystals have planes of symmetry and are divided into seven symmetry systems. The number of axes, their length, and their angle to each other determine the system to which a crystal belongs.  Opal crystalizes in the amorphous crystal system (trigonal-trapezohedral), without a particular crystal habit.


Color

Opal's color varieties are classified as: "Black" (black body color), "Semi-Black" or "Grey" (dark body color), "Light" (between semi-black and white), "White" (very light body color), and the rare "pineapple" psuedomorphic opal from White Cliffs in NSW.

Opals vary widely in body color, with white the most common. Black is considered the most valuable as it enhances and accentuates the play of color (opalescence).  Fire Opal (yellow, orange or red), is often faceted and can resemble Ruby. Green and Blue Opals are very rare.

Combining body color and play of color (opalescence) we are faced with infinite possibilities, so pricing is complex. Size is also a factor with the carat price for larger stones accelerating accordingly. The intensity of the play of color and the extent to which it covers the Opal's surface also count.

 
Cut

Fine Opal stones are cut and polished to round or oval cabochons or other softly domed shapes so as to display the best color. Cut is a very important characteristic of Opal, as the beauty of the crucial feature (i.e. color play) of the stone is dependent on its cut. The cut of the stone is the key to revealing its magnificence. First, the cutters remove the inclusions present in the stone with a diamond cutting wheel.  Next a soft dome shape is given in order to bring out the fine color play. After cutting, the finishing is done using sandpaper, and finally the polishing is done with the help of a wet leather wheel. Jewelry designers can get many desirable cuts or the shapes from this striking stone. Oval, circular and round cabochons are preferred as in these shapes the color play is displayed at its best. Some other popular shapes are teardrop, square, rectangle and triangle etc. Only the very finest qualities of Fire Opal are suitable for faceting. 


Treatments

Opal is a soft stone and therefor is occasionally treated or impregnated with colorless oils, plastic, resin or wax which act as a bonding agent, reduce the visibility of the inclusions and improve the overall clarity of the stones. Black Opal is occasionally treated with chemicals, smoke, or dye.  Opals are alsio sometimes backed with foil, black paint or laquer.  Thin opal is often made into doublets, or triplets by covering the back and front.

Since opals are not only soft, but also have a significant water content, they require special care.

AJS Gems fully discloses any and all treatments to our gemstones.
 

Sources

Opal began its formation 15 to 30 million years ago, during the tertiary period. Starting out as a liquid, the slurry seeped through sedimentary layers of earth, settling within impervious clays at a depth of 20 to 30 metres. Over the course of millions of years, the liquid slurry crystalized, becoming precious opal.

This gemstone is found all over the world; however the precious variety of Opal has mainly been mined in one specific spot in the world – Southern Australia.  Southern Australia is renown as the Opal capital of the world and has been responsible for up to 95% of the opal mined. But recently a major find of precious opal in Ethiopian has changed the opal market, with significant quantities of high grade material coming on the market.

There are also known Opal deposits in Brazil, the Czech Republic, England, Honduras, Mexico, South Africa, and the United States.

The primary source for opal is Australia's sedimentary sandstone, shale, and limestone deposits of the Great Artesian Basin. Many of Australia's famous opal mines such as Lightning Ridge and White Cliffs in New South Wales, Quilpie, Yowah, and Opalton in Queensland, and Andamooka and Coober Pedy in South Australia produce the finest gem-quality opal in the world.

 

Opal Sources Australia               Opal Mine Australia


Opal mining in the outback regions of White Cliffs and Coober Pedy is a chaotic and disorganized affair. With no centralized oversight, miners spread out across the plain, digging holes at random, leaving behind a strange landscape of mounds resembling the surface of the moon.

Opal that is mined from Australia's Andamooka mine is considered to be some of the most durable and stable opal due to its low water content. Fire opal is found in Central America, South America and the United States (Idaho and Oregon), typically within cavities formed in volcanic lava flows.

 

Mythology 

Opal is derived from the Latin word 'Upala' and the Greek word 'opallios', both meaning “precious stone”.

The Roman scholar and famous author Pliny once described Opal as a gemstone that combines the best possible characteristics of the most beautiful of gemstones: the fine sparkles of Almandine, the shining purple of Amethyst, the golden yellow of Topaz, and the deep blue of Sapphire, “so that all all colors shine and sparkle together in a beautiful combination.”

In Greek mythology, Opal was believed to be formed from the joyous tears wept by Zeus after he defeated the Titans. It was also believed by the Greeks that the owner of Opal would obtain the power of giving foresight and the light of prophecy.

In ancient Arabic times it was believed that opals fell from the heavens in lightning, the flashes giving the stone its fire and flare.

It is said that Opal was part of Cleopatra's famous jewelry collection, and that she used the stone to attract the attention of Mark Anthony.

Opal is said to be a symbol of faithfulness and is believed to assist the wearer with finding true love. Opal is also believed to cure depressions and bring confidence to the wearer. Opal helps to open unused parts of the mind in order to increase creativity and mental capacities.

In past, it was believed that wearing this fascinating gem helps in finding the true love. Also it was considered as an icon of faithfulness and confidence.

Women in ancient times used to wear opal to protect their hair from graying. It was largely used for ritual magic.

Astrologers recommend different opals for different zodiac signs. Black Opal favors those having the Scorpio zodiac signs while Boulder Opal suits for those having Aries as their sun sign.

Opal helps in overcoming depression in life and diverts the energy in improving the positive traits. It enables the wearer to use his/her brain fully. 

 

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