GemNotes

Tanzanite Lookalike

A new synthetic produced for laser applications imitates tanzanite, according to research gemologist Martin Haske, owner of Adamas Gemological Laboratories in Brookline, Mass. Synthetic forsterite, whose additional cobalt content imparts the tanzanite-like blue/purple color, has been on the market six months.

Gemological identification should prove easy. Tanzanite has a refractive index (R.I.) range of 1.691 to 1.704. Forsterite, with an R.I. of 1.636 to 1.672, will show more obvious doubling. A 1-ct. forsterite, with specific gravity (S.G.) of 3.2, will look like a 1-ct. tanzanite (S.G., 3.38), but both will appear slightly larger than a 1-ct. diamond (S.G., 3.52). Durability should be similar; forsterite’s hardness is 6.5 to 7.0, the same as that of tanzanite. Forsterite is a member of the olivine mineral series, which includes fayalite and peridot.

A CSO for Sapphire?

Modern mining coupled with wholesale marketing may help a U.S. corporation become the Central Selling Organisation of the sapphire industry. ABFG (American Benefits Group), headquartered in New York City, has bought 37 concessions in Madagascar containing sapphire deposits. The company believes the properties provide the basis for supplying 20% of the world’s sapphire, enough to influence, if not control, pricing. Estimated total production is between $274 million and $2.75 billion.

Madagascar, which produces large quantities of fine gem material such as emerald, ruby, tourmaline, aquamarine, and garnet, has been described as the new Sri Lanka. Both countries produce a vast variety of gems from alluvial sources—loose gravels found in ancient river deposits. Gem sapphires are found in placer deposits, typically alongside other gem material such as apatite, amethyst, and sphene. Geological similarities between the two countries shouldn’t be a surprise—millions of years ago, when the world’s continents were joined as one, Madagascar and Sri Lanka were side by side.

Sapphires seem the most abundant Madagascar gems. The material, like the Sri Lankan, can be of very fine color, whether natural or heat-treated. The U.S. market is beginning to see some from a few gem wholesalers, but that could change dramatically.

ABFG has created a joint venture with the Menavi Group, an Israeli colored stone manufacturing and trading company located in Ramat-Gan. The joint venture, Total Gem Management Ltd., expects to channel a sizable, steady, long-term supply of both rough and cut sapphires through its offices in Israel, New York, and Thailand. ABFG believes its mine-to-market concept will translate into a consistent and controlled supply of sapphire to the industry.

“What makes the Madagascar supply special is that it covers the complete range of sapphires—from the most exclusive gem qualities to inexpensive commercial goods,” says Menahem Sevdermish, one of the Menavi Group’s two principal owners. “Australia, for example, produces a large amount of sapphires, but only in a limited quality range. In Madagascar, on the other hand, you see everything, including stones that compete with the very best of Kashmir and Sri Lanka.”

Retail sales are available through ABFG’s Internet site “shopping mall” at www.rodeoisland.com. The mall’s first “tenant” is www.thegemstore.com, which shows a selection of karat gold jewelry set with Madagascar sapphire and emerald. One item, an 18k yellow gold ring set with a marquise sapphire and round brilliant diamonds, is priced at $299.

Camcorder Adapter for Recording Take-ins

Now you can record take-ins for repair and appraisal using your video camera and microscope. Jeff Wildman, owner of GemPro, a division of Wildman Instruments in Sunriver, Ore., has developed a coupler that attaches an ordinary camcorder to a microscope. “It allows your customer to see exactly what they have brought to you for repair or appraisal, while you record both the image of the jewelry and the conversation between you and your client,” says Wildman. “Everybody’s been wanting to use their own video camera with their microscope, especially now that everybody’s going digital.”

Wildman says the most popular digital camcorder is the Sony Mavica, which he says is particularly good for taking close-up pictures “that suit 99% of the people in the business.” Now, however, jewelers want to take pictures through a microscope. “We sell an adapter that clips most Sony camcorders to the eyepiece,” Wildman says. The Mavica also has a removable floppy disk. “Now you can take pictures through the scope, pull the disk, and load it into your A-drive, and the picture is right there to place onto appraisals,” says Wildman. For information, contact GemPro at (541) 593-9663.

Introducing Synthetic Blue Diamonds

Ultimate Created Diamonds of Golden, Colo., has introduced another first, a commercially available, fancy intense blue-colored synthetic diamond. The extraordinary color equals the best natural blue diamonds ever discovered. Sizes and quantities are still limited. Prices range from $2,000 to $5,000 per carat, subject to availability.

Both synthetic and natural blue diamonds are type IIb—boron imparts the blue color and electrical conductivity. Unlike natural diamonds, synthetic blues phosphoresce after exposure to short wave ultraviolet—for hours! They also exhibit sizable inclusions of the metallic nickel-iron residual flux. A neodymium magnet, available at electronics supply stores for less than $20, will attract synthetic diamonds that contain visible flux.

Oregon Sunstone: The Glittering Prize

Say the name labradorite and what automatically comes to mind is a gray, semi-translucent rock, with patches of floating peacock-colored iridescence. Substantial quantities of this common type of labradorite are found in—where else?—Canada’s Labrador province. It’s so plentiful, in fact, that it’s not uncommon to see huge, polished, marble-like walls of labradorite in banks and other big-city office buildings. But mention the name labradorite to a native Oregonian, and he will describe something else—an orangy-red transparent gem, with glitter. It’s sunstone, Oregon’s state gem.

Oregon sunstone comes in a variety of colors, from nearly colorless to pale-green, orange, and red. It can show strong pleochroism, whereby the gem’s orientation determines the color. But sunstone’s rarest property is its “schiller,” a sparkling effect created by layers of included native copper. It’s been said that the schiller is the sole reason for the gem’s name.

Two areas in Oregon, about 100 miles apart, produce sunstone. The Ponderosa area lies in the north of southeastern Oregon’s Harney county. The Plush area is centrally located in Oregon’s south central Lake County. Native Americans first found the gems—on the ground, as many are found even today. Major commercial application didn’t begin until the last half of this century.

The Dust Devil Mine, one of the most successful to date, began when Terry and Jude Clark and Don and Patsy Buford uncovered three abandoned sunstone claims near the town of Plush in the high desert of southeastern Oregon. They staked claims in February 1992. Mining season averages six months, and it was just getting dry enough in July to start operations again. The Bufords hope to mine until mid-October. (Winter temperatures can drop below zero.) Plush area sunstones can be mined with pick and shovel, beginning at the surface and continuing through partially decomposed rock approximately 24 feet deep.

Of the dozen or so small operations in the area, only a handful are mechanized. The state has preserved a large area as public property to prevent a small number of mining corporations from controlling the gem field. Dust Devil Mining Co. is a mile from a public collecting area. Buford predicts that reserves on his claims should last 10 to 15 years.

On the Ponderosa, you won’t find Ben, Adam, Hoss, or Little Joe, but you will find some of the finest sunstone in the world. Four claims are situated in what many believe is the volcanic area that spawned the lava-flow sunstones. Uncovered during construction of logging roads in 1980, the Ponderosa area produces incredibly saturated reds with lots of schiller.

Mine owner Larry Gray reportedly sold the property to a mining investment firm, Janus International Inc., for $8.5 million last summer. The conservative reserve valuation of the Ponderosa Mine is more than $100 million.

Oregon sunstone is typically red. Many gems are eye-clean, with an orangy-red body color. Rough material is unusual; a typically colorless or near-colorless outer skin surrounds an inner green layer and a central red core. (Some are considered “watermelon” sunstones.) There are bluish-greens as well as bicolor red-and-green gems, but these are rare.

Joy Bower of Sunstones ‘n’ Such in Caldwell, Idaho, says the Ponderosa claims yield stones showing “deep, deep wine-red colors, bluer, deeper greens, and mainly schillers.” Plush area sunstones appear in “peaches and greens,” with greater clarity and a wider range of colors.

The most valuable sunstone is pinkish-orange faceting material with evenly distributed copper inclusions—considered the “true” sunstone. When the schiller is parallel to the table, it creates a noticeable flash over the entire face of the stone. It’s said that if the inclusions are at a slight angle from the table, schiller is visible throughout the entire stone, imparting a three-dimensional glitter.

Many purists believe the name sunstone should be applied only to transparent labradorites that show schiller. They prefer the term “heliolite” for non-schiller varieties. (In Greek, helios means sun, lithos means stone.)

Labradorite by any name has a hardness of 6.5 to 7, a refractive index of 1.55 to 1.58, and a specific gravity of 2.70. Because of its 42º critical angle, it’s been suggested that a pavilion angle of 44º provides the best appearance.

Dust Devil began selling Oregon sunstones at the Tucson gem shows in February 1996. Will Cox (www.gemcarver.com) took first place that year in the American Gem Trade Association’s prestigious Cutting Edge Awards with a carved sunstone (his second). Other award-winning cutters and carvers have used Oregon sunstone in competition.

Prices Per Carat

Yellow or “water clear” $15-$25
Pink schiller $18-$25
Light-red or -green $60-$75
Silver schiller $100-$150
Medium-red or -green $75-$100
Bicolor and tricolor $175-$300
Dark-red or -green $175-$300
Intense dark-red or -green with excellent cut, clarity, and color saturation $350-$500
Dichroic stones $350-$1,000
Color-change stones $350-$1,000
Collector stones $200-$2,000
Carvings from 5 cts. to more than 100 cts. $50-$500
Cabochons are typically 60% of the price of faceted stones of the same color.

Price chart courtesy of www.dustdevilmining.com