Geolat & Associates "In The News"
HOW TO BUY OPAL
by Patti J. Geolat
Say opal to most people, and the image that comes to mind is a white stone flecked with greens and blues. In fact, this is just the most common, inexpensive variety of opal. Until you have seen a spectacular black opal that sells for $10,000, you do not know the colorful drama this gem is capable of. Because every opal is unique, with a color pattern all its own, the stone might be the least understood of all precious gems. But if you do your homework, you can walk away with a gem as dazzling and richly hued as the better-known ruby or emerald -- and that costs a lot less. A few basic guidelines can help you judge the quality of an opal, and whether the price is right.
COLOR SCIENCE
Just how does nature create those shifting rainbows that give opal its unique appeal? The play of color is caused by diffraction, the same principle that creates the iridescence on the back of a CD. Opal is made up of tiny particles of silica, arranged together in closely packed spheres. In fine opal, these spheres line up perfectly in a three-dimensional grid that diffracts light, in the same way that grooves on a CD do. Each different plane of color you see in the opal is a grid of same-size spheres lined up just right. Different color wavelengths are scattered by different size spheres. Bigger spheres create longer red wavelengths (as well as all the other colors in the spectrum as the opal is tilted). Smaller spheres will only create blue and violet colors.
SUPERIOR SOURCE: AUSTRALIA
The finest opal in the world comes from Australia. This country is actually the only producer of black opal, the most magnificent of all opal varieties. But just because the best opal comes from Australia does not mean you will get the best price if you buy it there. Gemstone prices are a matter of supply and demand. The tourist trade in Australia jacks up demand for opal inside the country, so prices can actually be higher than you might find elsewhere.
ABCs of EXCELLENCE
When experts assess opal, they start with its body color. This refers to the overall base color of the stone, versus the shifting play of color that makes every opal distinct from another. The most valuable opal is one that displays its color patterns the most dramatically. The darker an opal's body color, the more vivid its play of color. Thus black opal is more costly than the white (also called light) gems, with body color ranging from colorless to medium gray. The next factor to consider is transparency. All opals, regardless of body color, will be transparent, translucent, or opaque. When a stone has lots of transparency with clear, sharp colors visible on the surface as well as within, it is called crystal opal. Though transparency increases the value of a white opal, it can decrease a black stone's worth. Opaqueness is what will make a black opal's internal colors pop.
The kind of colors, or hue mixture, an opal exhibits is critical and can send its price soaring or plummeting. Red is the most prized color in opals, followed by orange, yellow, green, blue, and violet. No matter what its color play, however, an opal must have an overall brilliance to be considered valuable. Red patterns in an otherwise dull gem, for example, will not net the premium of a bright opal with more run-of-the-mill colors like greens and blues.
"A 1.01 carat white opal set in platinum with 1.02 carat diamond, $5,350. The brilliance and variety of color in the opal enhance its value. "
Specific colors are not only what connoisseurs want in a fine opal. How much color an opal has and how these colors are arranged into patterns is also key. Broad, well-defined patches of color (called "rolling flashes" in the trade) are preferred to the small pinfire. Also desirable is what is known as a color bar -- a layer of color different in hue from the layer above or below it.
Far left: Pinfire opal, $10,000. Though broad swathes of hue are best, pinfire that is bright and well-distributed can carry a high price tag. Middle: Example of a color bar. Near left: The colors in this opal are very vivid but the lack of hue in the rest of the stone minimizes its value.
OPAL VARIETIES
Black opal: This variety of opal refers to a stone with a body color from medium gray to black. Unlike other gems that might be mined in various locations throughout the world, black opal is found exclusively in Australia. Price: For a stone under 10 carats, expect to pay anywhere from $200 to $20,000 per carat. The finest-quality exhibits wide patches of coveted colors like red or orange.
Boulder opal: With an appearance much like black opal but considerably less expensive, this variety is considered by some to be the poor man's black opal. Boulder opal, however, is actually a lovely and relatively rare variety in its own right. It gets its name from the boulders of sandstone in which it is found and that cutters leave on as a natural backing. Price: Boulder opal is priced per stone and not per carat. For a stone under 10 carats, the price can be as inexpensive as $10 and as high as $20,000.
Top: Side view of an opal triplet, with translucent top, black backing, and finally, the gem itself.
Bottom: Opal doublet earrings with 18k yellow gold and 40 carats of diamond, $3,750.
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Crystal opal: The next grade in quality to black and boulder opal is crystal opal, which can have a body color from light to dark. The name refers to the glasslike appearance of the stone, not the structure. Price: For a stone under 10 carats, expect to pay from $10 per carat for a lower quality opal to $6,000 per carat for the best quality.
White opal: Thanks to Australia's rich deposits, white opal can be found in abundance, though only a small portion of it is fine enough for the true connoisseur. Price: Milky opal with a pale color pattern is ubiquitous and can virtually be had for pennies. Expect to pay a steeper price, however, for fine-quality white opal, with translucency, brilliance, and an interesting color pattern -- anywhere from $200 to $400 per carat for a stone under 10 carats.
Doublets and Triplets: When good-quality opal is too thin to be made into jewelry without becoming damaged, the slivers are bonded to a black backing for support. The resulting opal is called a doublet. If the opal is especially thin, it may also get a colorless top in addition to a backing -- a three-layer arrangement called a triplet.
Price: Doublets and triplets give you the look of a black opal at a fraction of the price. Because these are assembled stones, they are sold per piece versus per carat. Smaller stones can be as inexpensive as $10 to $30, with larger, more spectacular stones selling anywhere from $400 to $500.
ON THE LOOSE: BUYING UNMOUNTED OPALS
Whenever possible, it is best to buy gems before they are mounted -- that way you can really see what you are getting. Mountings, ideally, are designed to enhance the beauty and form of gemstones, but they can also be used to mask flaws or to make a gem look bigger than it actually is. The black opal in the ring in the photograph at left appears very fine in its setting. But if you look at the back of the ring, you will see the mounting is enclosed. When we removed the opal from the setting, we found it was not as fine as it appeared. The stone was thinner, and opals that are thin have a greater risk of being damaged. In addition, the opal had lots of area without color. Color, as we have seen, is the main factor that adds value to the stone.
Opal DOs and DON'Ts
Some opals have structural weaknesses that make them prone to cracking after prolonged exposure to heat and dryness. (Boulder opals are an exception. Their nature stone backing gives them exceptional durability.) Once an opal has "crazed" (cracked), it has virtually no value. However, with a few precautions, you can enjoy your opal for a lifetime: DO buy an opal from a reputable dealer, who often will "cure" new opals by letting them sit for long periods before selling to weed out any that crack. DON'T expose the gem to severe temperatures or dramatic changes in temperature. DON'T store (for lengthy periods) in an unopened safety deposit box. DO clean regularly with warm soapy water and rinse in clear water.
Geolat and Associates is a firm of independent fee appraisers specializing in the valuation of fine art, fine craft, 19th and 20th century furniture, Avant- garde design, china, glass, silver, photographs, gems and jewelry (antique, period and contemporary) as well as fine jewelry by internationally recognized designers and artists for private and public clients worldwide. Website: www.geolat.com
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Patti Geolat, founder & CEO of Geolat Companies, is a widely known authority on appraisal, brokerage & sale of fine jewelry. Her clientele includes many of the top jewelry houses globally, as well an extensive network of private & industry collectors. She has a reputation for excellence, confidentiality & ethics in the private world of jewelry and gemstones, giving her access at the highest levels. 