By Russell Shor

Cutting, selecting and mounting gemstones to create a suite of jewelry is an exacting process, and sometimes years of work are required to assemble a sufficient quantity of appropriate material.

The lead article in the Winter 2004 issue of Gems & Gemology, by Robert E. Kane, chronicles the creation of a magnificent suite (necklace, bracelet, ring and earrings) of peridot jewelry, from the discovery of the gem deposit in Pakistan to the manufacture of the individual pieces.

A major deposit of large, fine-color peridot was discovered in the mountainous Sapat Valley of northern Pakistan in 1994. Significant amounts of the gem material began to enter the international gem market and the discovery thrust peridot into the mainstream jewelry industry. The fact that the Pakistani material is larger and more uniformly colored than goods from other sources created the opportunity to assemble this jewelry suite, which contains more than 350 carats of peridot.

After explaining the selection of the rough, the article describes the marking, preforming and faceting processes in detail. The goods chosen for the jewelry suite were preformed to their basic shapes by a master preformer, then turned over to a skilled European-trained cutter for faceting.

Once the 54 gems were finished – all Asscher cuts except for the necklace center stone – they were sorted and compared to ensure exact matches. Some were re-cut slightly to achieve that result. The final suite ranged from 3.57 to 18.30 carats. Van Cleef & Arpels began work on the designs (in their Paris studio) and settings (in New York) after the peridots were faceted.

Van Cleef & Arpels created simple, modern-but-classic designs in platinum, setting small, precisely cut baguette diamonds between the peridots of the necklace, bracelet and earrings. The baguettes set into the necklace had to be modified to accommodate the curve of the piece. In addition, the 24 small diamonds set into the ring, which holds the 18.30 carat peridot, had to be fashioned to the proper angles to fit perfectly into the settings.
 
Chart Update
The Winter G&G also offers a comprehensive, updated chart on commercially available synthetic diamonds grown by a high-pressure/high-temperature (HPHT) technique.

The chart, created by GIA Director of Research Dr. James E. Shigley and co-authors, provides a photographic overview of the common identification characteristics of the synthetic diamonds in the marketplace. The information is based on samples from all known sources of production collected at GIA during the past 25 years, encompassing approximately 500 synthetic diamonds.

The information and photos are grouped into two categories: common features that have been seen in most HPHT-grown synthetic diamonds, regardless of color or cause of color; and specific features that are related to whether the synthetic diamond is “as grown” or has been subjected to post-growth treatment to change its color.

Another article focuses on a new, less-costly detection process for Be-diffused treated sapphires known as laser-induced breakdown spectroscopy (LIBS).

The article, by Michael S. Krzemnicki, Henry A. Hänni and Roy A. Walters, describes how LIBS can offer a reliable alternative for Be-diffusion testing. The equipment costs only 10–20 percent of the LA-ICP-MS (laser ablation–inductively coupled plasma–mass spectrometry) units previously used by some labs for this procedure, and is much easier to use. The LIBS method can detect beryllium down to 2 to 3 parts per million – what is believed to be the minimum amount of beryllium necessary to create yellow color centers in sapphire.  A disadvantage is that, like the other advanced techniques used, it leaves very small (about 0.1 mm) pits on the surface of the gemstone.

Lab Notes
Faceted apophyllite is extremely rare because of the gem mineral’s susceptibility to heat damage. Therefore, the GIA Lab examined a near-colorless 6.28 carat oval modified brilliant cut from Poona, India recently.

The West Coast Lab recently examined a 0.12 carat Fancy Intense purplish pink diamond that displayed apparent magnetism. After tests concluded it was natural, staff discovered a magnet seemed attracted to dark material exposed in cavities along the girdle. Testing revealed that the dark material contained iron, which was probably left over from the cutting process. Although the magnetic reaction was similar in intensity to that of a synthetic diamond with metallic inclusions, cleaning would probably render this diamond “non-magnetic.”

The West Coast Lab also examined a 0.32 carat near-colorless round brilliant diamond. Upon testing with the DTC DiamondView, it was determined that it was synthetic. If it was natural, its clarity would have been in the VS range and its color approximately I, making it a very rare example of a high-clarity, almost colorless synthetic. Microscopic examination did find tiny metallic-appearing inclusions.

The East Coast Lab recently examined three strands containing a total of 87 “golden” South Sea cultured pearls. The color appeared to be an unnatural orangy yellow with an unusual pinkish cast under some lighting conditions. When examined with 10× magnification, all of the cultured pearls showed slightly mottled nacre with small raised spots and patches. They also exhibited visible signs of having been dyed, including an unevenly distributed color and small concentrations of a deep red dye. 

Gem News International
Recent Gem News International reports describe an orangy yellow natural diamond that contained a high concentration of nickel, and several interesting colored stone finds, including adularescent chalcedony from Iran; clinohumite from Tajikistan; sapphires from Afghanistan, Pakistan, and Canada; and a new gem material from Madagascar that is a mixture of cristobalite and opal.