By Russell Shor

The Winter 2007 issue of G&G

GIA researchers Wuyi Wang, Matthew Hall and Tom Moses, in conjunction with Apollo Senior Scientist Joshua Tower, examined gemological and spectroscopic properties of 43 "as-grown" synthetic diamonds, both faceted and rough.

This new generation of Apollo-produced synthetics showed significant improvements in size, color and clarity over those examined by GIA researchers for a report published in the Winter 2003 issue of G&G. In addition to colorless and near-colorless material, Apollo also provided fancy orange-to-pink synthetic diamonds to study. While the samples were comparable in appearance to natural diamonds, all could be identified using a combination of gemological and spectroscopic properties.

Fall 2007 Issue
The Fall 2007 issue of G&G chronicles how natural forces, economic events and advances in culturing techniques converged to transform the cultured pearl industry from a single producer with a single product to a global business offering a large array of choices.

The report by GIA senior industry analyst Russell Shor describes how at the beginning of the 1990s, Japanese-produced white, round akoya cultured pearls accounted for some 70 percent of world pearl production, and Japanese distributors controlled a far greater percentage of cultured pearl sales. Within a decade, the vast majority of the market was composed of South Sea cultured pearls from Australia, Indonesia and the Philippines; black cultured pearls from French Polynesia; and attractive freshwater cultured pearls from China.

A second article takes a look at nailhead spicules, which have traditionally been an identifying characteristic for hydrothermally grown synthetic emeralds and quartz, and similar looking inclusions seen in natural gemstones.

Researchers Gagan Choudhary and Chaman Golecha, of the Gem Testing Laboratory in Jaipur, India, examined a natural emerald and blue sapphire that had true nail-head spicules that developed during rapid growth – the same cause as in synthetic stones.

The article offered detailed photographic evidence of the inclusions along with gemological data showing the gems' natural origins. As a result, such inclusions cannot be considered conclusive proof that a stone is synthetic.

The Fall issue's Rapid Communications section features a report on two newly discovered deposits of copper-bearing (Paraíba) tourmaline in Brazil's Paraíba State.

One deposit, the "Glorious Mine," is very close to the locality where these "electric" blue gems were originally discovered. While some 500 grams of tourmaline have been mined there since production began in March 2006, only approximately 200 pieces, totaling about 40 carats, have been of sufficient size and quality to be faceted. A second mine located nearby, Mineração Batalha, has yielded a number of bicolored (blue and pink-to-violet) crystals, but all the material found thus far has been too included and fragile for cutting.

The second Rapid Communication describes a 1.75-ct. Fancy green-yellow diamond with nickel-related spectroscopic features similar to those seen in high pressure/high temperature (HPHT) synthetic diamonds with a strong green component. Nickel, which is used as a catalyst in the growing process, causes a green color in some synthetic diamonds. This type 1a diamond was a rare natural diamond that was colored by nickel, however, indicating that the substance may be a previously unidentified cause of the green color in diamond.

Lab Notes, Gem News International
The GIA Laboratory examined an unusually large 201.18-ct. cat's-eye aquamarine that showed a very strong chatoyant band; a 25.87-ct. blue chalcedony in which dye was detected by ultraviolet-visible-near-infrared spectroscopy; an 8.54-ct. kyanite that bore a striking resemblance to blue sapphire; and several interesting diamonds.

One diamond was actually two: A pendant containing an apparently large yellow pear-shaped diamond was disassembled and the large "single" diamond was actually two smaller diamonds set in a "piggyback" arrangement.

The Lab also examined a diamond – purported to be D color, IF clarity – accompanied by a photocopy of what appeared to be a GIA report. Testing of the stone, however, proved it was HPHT treated. Further examination revealed that the laser inscription of the GIA report number was of poor quality, and that the stone weighed 0.0028 carats more than the diamond listed on the report. The diamond was returned with a new report and the words "HPHT PROCESSED" inscribed on the girdle.

Gem News International took a detailed look at the large diamond mine being developed in Saskatchewan, Canada, which may produce some 200 million carats over an anticipated 30-year life span. Other items include a new find of color-zoned axinite from Pakistan; multicolored fluorite from Brazil; blue-green opal from Iran; a possible diamond inclusion in quartz; new sources of ruby in Pakistan and Afghanistan; and large beryl triplets imitating Colombian emeralds.