GemNotes

CSO Cuts Sights; Reports Lower Sales for 1997

De Beers’ Central Selling Organisation reports 1997 sales of rough diamonds totaled $4.64 billion, down 4% from 1996. First-half sales actually rose 5% to a record $2.88 billion, based on trade expectations of good retail sales worldwide. But second-half figures fell 16% in light of continued recession in Japan and emerging economic and currency problems in Korea, Taiwan, Thailand and other South East Asian countries.

The trend continued in 1998, as the January sight proved to be the smallest in seven years. Estimates put it at $270 million, roughly 40% of the January 1997 total.

CSO director Gary Ralfe notes that South East Asia represents 17% of world sales and that retail diamond sales in Japan – the world’s second largest diamond market – fell by 20% last year. Diamond imports to that country declined by 30%.

A CSO statement summarizes, “The reduction in retail sales in those countries, the impact on trade confidence of this changed economic situation and the high level of trade inventory as a result of buoyant rough diamond sales in the first half of the year, have meant that the CSO has had to reduce its supply to the market to support the trade in what has become a difficult situation.”

It notes further that its 1997 inventory did not include any supply from Argyle, since that contract ended in 1996, and supply from Russia was lower during the period before the Russian trade agreement was renewed. In addition, Angolan production and Russian stockpile sales were lower in 1997 than in 1996. “The CSO’s control of the supply side of the industry has therefore improved over the last 12 months,” it says.

CSO sales of rough diamonds (in billions of U.S. dollars)

1988 $4.172
1989 $4.086
1990 $4.167
1991 $3.927
1992 $3.417
1993 $4.366
1994 $4.250
1995 $4.531
1996 $4.834
1997 $4.640

New Demantoids from Russia

Reports of a new deposit of Russian demantoids will cheer those who remember the original Ural gems. These new demantoids are as fine as the old ones and can be used not only for new jewelry, but also to restore estate pieces in which demantoids have been replaced with other, lesser value gems.

Demantoid is one of the rarer and more beautiful gemstones. Its dispersion, fine color and clarity made it a favorite in the Art Nouveau and Art Deco periods. Discovered in the Ural mountains of Russia in the 1850s, it basically was played out by the early 1900s and nothing quite like it had been seen since. This new deposit could become one of the most important finds of the century.

Bill Larson of Pala International recently returned from Russia with well over a dozen matched rounds, along with another dozen-plus single ovals and rounds, ranging in size from three-quarter carat to over three carats. Colors range from light to medium-light, moderately strong, yellow-green to dark vivid green. Dispersion is excellent on the lighter tones and less saturated colors, but tends to disappear once the color becomes saturated at a medium-dark, strong, very slightly yellowish-green. They have the classic “horsetail” inclusions.

Prices range from $1,200 a carat for light saturated gems to $3,000 a carat for medium-dark, vivid greens in carat sizes. – Gary Roskin

DE BEERS OPENS CANADIAN OFFICE

Canada’s diamond production could account for 10% of the world total within five years, said De Beers Chairman Nicholas Oppenheimer at the opening of the company’s first representative office in Vancouver, B.C. That office, he added, recognizes Canada’s importance as a diamond mining country.

De Beers has been represented in Canada for many years by Monopros Ltd., its Toronto-based, wholly-owned prospecting company. Monopros has discovered more than 100 diamondiferous kimberlites on its own property or in partnership with other mining companies. Its role will continue and be strengthened by De Beers Canada Corp., whose managing director is George Burne.

“Being in Vancouver puts us close to the considerable activity now underway in the North West Territories and the rest of Canada,” said Burne, “and will enable De Beers to take a more active role in Canadian mining and prospecting.”

Synthetic Moissanite: easy id

I recently examined some synthetic moissanite from C3 and can say not only that it is a very good diamond substitute, but it also is easy to identify – with a 10X loupe!

As a diamond substitute, it has a lot going for it:

  • Its dispersion reading is higher than diamond’s (0.104 for moissanite vs. 0.044 for diamond), giving it more noticeable “fire,” especially in melee.

  • Its refractive index also is higher, helping it stay brilliant even longer than diamond when it gets dirty and greasy. CZ, on the contrary, loses its brilliance after only a few days of collecting dirt and begins to look like a diamond substitute.

  • Its hardness helps it maintain its polish long after CZ becomes scratched and dull.

Martin DeRoy, vice president of marketing for C3, and Reneé McCullen, director of sales, said their biggest concern is keeping down the cost of smaller stones. “At least now we’re talking weeks instead of months” to have product on the market, said DeRoy in relief. Indeed, they showed me tennis bracelets, single stone rings, earrings and loose goods at an off-site room during the mid-January JCK Show in Orlando and planned to display material at the early February JA Show in New York City.

Moissanite is hard (91/4 to 91/2) and takes a good polish, so facet junctions look sharp. The cutting factory has done a good job with polish and symmetry, giving the stones the look of very well-cut diamonds. Clarity and color are excellent. The few stones examined with a 10X loupe were approximately VVS to VS in clarity and G-H-I in color (a close guess in a poorly lit room with no master stones).

But the material is obviously doubly refractive, with over .040 birefringence. So if you tilt it to the side and glance through the bezel facet towards the culet, you can easily see a doubling of facet junctions – something you’ll never see in diamond or CZ. Moissanite has been cut so that you don’t see the doubling through the table, as is common in zircon; this would make stones appear blurry or fuzzy. (For those unfamiliar with gemological properties and the use of a loupe, C3 markets Tester Model 590 for $525, which also identifies the product.)

Consider synthetic moissanite an opportunity, not a worry. It is something to consider if your customer wants a diamond look, but cannot afford the real thing. It costs somewhat more than CZ, but seems worth it for its longer-lasting brilliance and durability. The dispersion can overpower the diamond-like appearance of larger stones, but C3 is experimenting with different crown and pavilion angles to reduce the fire.

The firm currently is working on marketing plans. It may be able to take advantage of two marketing masters projects at the University of North Carolina and Duke University, which heard about C3 (a local company) and took as their theses the difficulty of marketing a synthetic diamond substitute. – Gary Roskin

New Black Opal Find In Australia

A promising new black opal deposit is reported in Wyoming, an area within the Lightning Ridge opal range. Gemline, a publication of the Australian Opal and Gem Industry Association (AOGIA), reports that more than 125 new claims in the Wyoming fields and surrounding areas have yielded some black opal of the quality of traditional Lightning Ridge blacks. Gems of larger sizes show good strong green, green/blue, green/orange and red. It is less flawed than material mined the past few years.

Peter Sherman, AOGIA vice president and owner of Sherman Opals of Sidney, says many claims have been made in this area on privately owned property. Most other Lightning Ridge claims are on government-controlled lands to which indigenous Australians have laid claim. Sherman expects the government to wait until after the Sidney Olympics in 2000 before making decisions which might cause Aborigine or settler outcry.

“Slowing Asian markets, the volatility of the U.S. and Australian dollar and the summer heat” have all played a role in declining opal sales, says Sherman. While some miners have stopped work only temporarily for the summer, others may shut down for a year or two, get a steady job in the city, then wait for the property dispute to be resolved and gem prices to stabilize. Sherman will be mining again after the summer heatwave ends, but he’s not certain who else will be back.

More than 1,800 people live permanently in Lightning Ridge, with a transient population of 6,000 to 8,000. The uncertainty of land ownership has made it impossible to sell homes or acquire mortgages within 50 km radius of the town center.

Heat treated Mong Hsu Burmese Ruby vs. Flux synthetic

Only a decade ago, if you were looking for the most beautiful natural red rubies, you sought stones from Burma. Today, you still may seek Burmese quality, but if you find Mong Hsu Burmese rubies, the color is anything but natural.

Super heat treatment not only gives Mong Hsu stones their spectacular color, it also produces inclusions which look similar to those in some laboratory-produced flux synthetics.

Natural vs. heat treated color. Natural color Burmese rubies were, and still are, the rarest, costliest and most beautiful. A large one – anything over 5 carats – could run well into the quarter-million-dollar range. To identify them, a gemologist looks for the diagnostic transparent rounded crystals and nests of rutile needles (“silk”). If these gems are heat treated, the crystals acquire an accompanying strain halo fracture and the needles dissolve into small “dots” of rutile.

Many of the Burma rubies seen on the market today are from Mong Hsu, a deposit 300 km southeast of Mogok and 250 km east of Mandalay. These crystals come out of the ground with a dark saturated purple-red hue and an unusual very dark blue core. To produce the traditional and sought-after Burmese color – a medium to dark, very slightly purplish, vivid red – Mong Hsu rubies are heated at way beyond the typical 1350°C for several hours.

Some of this heat treatment occurs at the mines, but most is performed in Thailand. At the mine, rough crystals are placed in a crucible filled with borax powder to prevent cracking. The crucible is put into a steel drum, a makeshift version of a kiln. Wood and coal are placed in the bottom of the kiln, and the fire’s temperature is raised to over 1300°.

And it works; the rubies look great. Many would call their color some of the finest to come out of Burma. But many jewelers have no idea that these rubies have been heat treated.

But is it synthetic? Heat treatment of Mong Hsu rubies, unlike any other natural rubies, creates inclusions which look just like synthetic “flux fingerprints” – high-relief white drippy globules of flux. That’s why I was confused the first time I saw a Mong Hsu ruby; it looked just like what I used to teach about flux synthetics.

If these fingerprint-like structures were the only inclusions, it might be impossible for standard gemological tests to prove natural or synthetic origin. The key may lie in the core. Because of the chemical growth and crystal structure of the rough crystals, Mong Hsu gems have a central hexagonal blue core. Heating the core drives out the color, but the core takes on a hazy appearance. Under magnification, this haziness appears to be made up of little “fuzzy” inclusions – shaped almost like asterisks. Because heat treatment leaves behind this hexagonal or angular fuzzy cloud, we are able to identify stones as heat-treated natural ruby.

When you first look at a heat-treated Mong Hsu ruby, you too will wonder if the inclusions you see are the drippy white flux commonly referred to in most gemological texts. Photos in The PhotoAtlas of Inclusions in Gemstones show the flux product and look just like Mong Hsu ruby – without the inclusions from the central core.

Fluorescence is a strong indication. Burmese ruby, heat treated or not, fluoresces strongly to ultraviolet light. Chatham synthetic flux rubies do not fluoresce and other flux-processed rubies, such as Ramauras and Kashans, show much less fluorescence than Burmese rubies. But inexpensive flame fusion synthetics can give the same reaction to UV as Burmese ruby.

So only through microscopic examination, which reveals the fuzzy angular core, can you be sure to distinguish Mong Hsu ruby from a flux product. – Gary Roskin

GIA SYMPOSIUM PLANS AT FULL SPEED

The Gemological Institute of America is in the final stages of lining up speakers, poster session presenters and sponsors for major events at its 1999 International Symposium, to be held June 21-24 in San Diego, Calif.

Dr. Vince Manson, architect for 1999, is excited about this historic gemological event. “What is the full experience going to be?” he asks. “Of course, the gathering of the top leaders of today with the sharpest minds in the business, talking about where we are and where we are going. Meeting tomorrow’s leaders, discussing the important issues while enjoying the splendid surroundings.”

The main symposium program, which focuses on the theme “Meeting the Millennium,” will feature technical sessions and panel discussions on a variety of topics of interest to all members of the gem and jewelry industry. More than 100 speakers and panelists will be selected to share their global views on gemological, socioeconomic, and geopolitical concerns relevant to the new millennium. Maurice Templesman will be the final keynote speaker.

AGTA Brochures Cover Enhancement

The American Gem Trade Association has two new brochures.

Gemstone Enhancements: What You Should Know tells customers about enhancement of amethyst, aquamarine, citrine, diamond, emerald, cultured pearl, ruby, sapphire, tanzanite, tourmaline and blue topaz.

The Consumer Guide to Emerald brochure explains traditional treatments in today’s market.

For prices and information on customizing large orders, call AGTA at (800) 972-1162 or (214) 742-4367.

March Birthstones: Aquamarine & Bloodstone

March has two birthstones, aquamarine and bloodstone. Aqua, a relative of emerald, is a transparent greenish blue beryl. Bloodstone, an ornamental chalcedony from India, is a translucent to opaque micro-crystalline non-varietal green quartz with red spots or patches of jasper chalcedony.

Its relative hardness and clean transparent quality have made aquamarine quite fashionable in designer/artist/ carver circles. It’s often shaped into traditional emerald cuts, round and oval brilliants, of course. But because it comes in good qualities and large sizes, modern carvers use aqua to create many fantasies, while traditional artists turn it into snuff bottles and other ornamental objects. Aquamarines range from the very small to substantial (50- to 100-lb. or more) cuttable crystals. A hardness of 71/2 allows carving and polishing without too much difficulty, yet maintains a very nice luster.

Bloodstone is an ornamental gem with a much smaller following. Its popularity dates back to the time of the Crusades. Bloodstone became sacred to Christians as its folklore signifies the blood of the crucifixion of Jesus on a field of green.

Those who created the list of birth gems obviously realized that not many men will wear aquamarines. Its light saturation and hue have little male appeal. Bloodstone, on the other hand, is seen mostly in bezel-set yellow gold men’s rings. Bloodstone actually was a best seller at last year’s JCK Las Vegas show for Gem Shapes Designs of Sausolito, Calif. In Gem Shapes’ men’s jewelry, the historical aspects of the gem influence the design of the mounting. Since the story of bloodstone has historical religious overtones, the mounting is accented with religious artifacts.

Color. Translated from Latin, aquamarine means “sea green” or “the color of the sea.” In Gems, Webster and Anderson (two well-respected British gemmologists) describe aquamarine as “a name which means sea-water,” then go on to say that its color “is a clear sky-blue.” Gemologists and jewelers often use nature to describe the color of gems. But likening aqua to the sea and sky has confused gem lovers for centuries. Just what is aqua supposed to look like?

Those born in March might agree that the sky in March does take on the color of aquamarine. In the Northern Hemisphere, March is the end of winter, the beginning of spring. Clouds are wispy in the upper atmosphere, which dilutes the saturated blue color of the sky. It becomes a medium-light to medium tone, moderately strong, saturated, slightly greenish blue – a perfect match for many aquamarines.

These days, most people think of aquamarine as a straight blue. That’s because most aquas are heat treated to drive away any hint of green. Yet gemological purists say true aquamarine should have a touch of green in its hue. The Guide suggests the most valued color is a moderately strong, medium dark, slightly greenish blue. But the gemologically accepted colors span the entire range of sea and sky blue, from blue-green to slightly greenish-blue to blue.

March is the first month in which the representative gem is not found in a vivid saturated color. Top quality rubies are vivid red; top quality emeralds are vivid, very slightly bluish-green. But we expect aqua only to be bright in color (medium in tone), not vivid in saturation.

Bloodstone derives its color from large quantities of chlorite inclusions (a bright green magnesium-iron silicate) and small inclusions of jasper (a red varietal chalcedony). The purer its green and brighter its red, the more valuable and sought after is a bloodstone.

Color and source. Depending upon their origin, aqua colors can be quite unique. Aquamarine from Madagascar is a strong saturated blue. Nigerian material can be a heavily etched dark greenish blue, reportedly not heat treated. Afghanistan gems are typically a strong light to dark blue. Zambian aquas usually are much less intense and possibly slightly grayish in hue.

Jim Thornley of James Thornley and Associates in Massachusetts says you do see some gray in Zambian aqua under certain light, but they’re not all that color. He purchased a parcel in the late 1980s in which the colors were an incredibly deep, pure blue – and reportedly not treated in any way. One gem, which finished out “rather small” at just over 5 cts., was sold to the Smithsonian. John White, curator of the gem and mineral hall, says that although it is not very big, “it is the most beautiful [aqua] in our collection.”

Such “collection quality” Zambian aqua wholesales at about $900 a carat; “exceptionally fine” at $400-$550 a carat; and “fine” at $150-$250 a carat.

Mozambique aquamarines typically are medium dark blue. And aquas from Brazil, the largest producer, cover almost the entire range of color.

The most notable bloodstone comes from India, although Australia, Brazil and China have significant deposits.

Enhancements. Most aquas are heat treated to drive out the green. Actually, they’re driving out a yellow component; yellow and blue make green, so the color which remains is a beautiful medium to dark, moderately strong blue aqua. This process is accepted as standard trade practice. It is believed to be permanent, so a bench jeweler need not worry about the potential to change a gem’s color.

Irradiation also can cause a change of color, but the process evidently has not been used much.

As for bloodstone, most such ornamental gems are worn by men and frequently subject to hard wear. To stand up, bloodstone often is strengthened and stabilized through treatment with epoxies.

Gemology. Iron gives aquamarine its greenish blue color, while emerald, another beryl, is colored by chromium or vanadium. Aqua’s refractive index of 1.577-1.582 is close to that of quartz (1.544-1.553), but there is no natural blue quartz with which it can be confused. Synthetic spinel and glass substitutes are commonly seen aqua substitutes. Both are singly refractive, showing no doubling of back facets as you see in aquamarine.

Some very simple gemological tests will eliminate any confusion.

  • Use magnification to look for the doubling of back facets.

  • Use a Chelsea filter. This hand-held instrument allows only a narrow range of green and red wavelengths to pass through. If a gem is colored by cobalt or chromium, only red wavelengths are visible; if it’s colored by iron, green wavelengths show through. When used to separate spinel from aqua, pink or red will identify synthetic spinel colored by cobalt. (Rare cobalt-colored natural blue spinels also will turn pink.) Aquamarine, colored by iron, will show green.

  • Use a dichroscope, which also demonstrates doubly refractive gems, to differentiate these look-alikes. If a colored gem is transparent and doubly refractive, the dichroscope shows two different colors side by side. Aquamarine can show blue and colorless or blue-green and yellow-green. Singly refractive gems like glass and spinel show only one color at a time.

Aquamarine, like emerald, can have two-phase and liquid inclusions. It also can have long hollow or liquid-filled tubes. If cut appropriately, a gem with a substantial number of these tubes will show a cat’s eye.

Bloodstone is one of a number of varieties of chalcedony, which is a cryptocrystalline gem made up of submicroscopic fibers of quartz. It is the coloration or design of these fibers which creates the huge assortment of chalcedonies we see, such as banded agate, onyx, fire agate, dendritic agate, chrysoprase and carnelian. A few of the chalcedony members which are somewhat related to bloodstone are prase (a light to medium, slightly grayish green stone), plasma (a dark green gem) and chrysocolla (a blue to greenish blue chalcedony).

Synthetics. Aquas have a very complex chemical structure and are not easy to make, although they have been produced in the laboratory. The synthetic gems are expensive, very limited and of no concern to the retail trade.

Cost. Fine quality aquas in the 2-carat range are $50 to $250 per carat.

As is the case with most ornamental gemstones, prices for bloodstone are stated in grams or by size, not in carats. Fine quality bloodstones measuring from 5 x 3 mm to 20 x 15 mm can cost approximately $30 per piece or more. – Gary Roskin