By Russell Shor

The Spring 2006 issue of Gems & Gemology (G&G) will examine a now-rare material that has adorned people for millennia: tortoise shell.

From ancient times, people have used tortoise shell in jewelry, art objects and personal items such as combs and eyeglass frames. The material was extremely popular, from the 18th through the early 20th century, for more than 200 years. The quantity of tortoise shell on the market declined sharply in the last half-century with the invention of less expensive imitations and the passage of laws protecting sea turtles.

Because trade in antique pieces continues, however, it is important to be able to distinguish tortoise shell from the many imitations that have been used over the years. This article details tests to identify tortoise shell using both standard gemological procedures and advanced spectroscopic techniques.

The Winter issue of G&G

Winter 2005 Issue
The Winter 2005 G&G examines the distinguished career of Dr. Edward J. Gübelin, the gemological pioneer who passed away last year. Dr. Gübelin worked in the field of his passion for more than 65 years. He was renowned for his research on – and photographs of – inclusions in gems. Today, the systematic classifications he developed help gemologists determine a gem's identity and possible country of origin.

Dr. Gübelin authored 13 major books and more than 250 articles, frequently traveling to the world's most important gem localities to gather information firsthand.

The article features a detailed summary of his work on inclusions, using many previously unpublished photomicrographs; a timeline of his life; synopses of the books he wrote; and reminiscences from relatives, colleagues and friends.

The Winter issue also pays tribute to another beloved figure, Dr. Alfred A. Levinson, professor emeritus of geology at the University of Calgary, who passed away in December 2005.

Dr. Levinson was a longtime contributor, reviewer and editor for G&G. Before Dr. Levinson pursued his interest in gemology, he made important contributions to mineralogy (as editor of the Apollo 11 Lunar Science Conference proceedings and developer of the Levinson system for naming rare-earth minerals) and exploration geochemistry (as author of two textbooks and numerous articles). A Graduate Gemologist, Dr. Levinson co-authored 10 articles for G&G, in addition to serving on G&G's Editorial Review Board for more than a decade.

The Winter G&G also reports on a new type of hydrothermal synthetic emerald that has been marketed since the end of 2004. Called Malossi synthetic emerald, the material is produced in the Czech Republic using Italian technology.

The article explains how the emeralds are produced and offers well-illustrated, detailed descriptions of their distinctive gemological characteristics. Malossi synthetic emeralds can be separated from their natural counterparts on the basis of their microscopic features, chemical composition and mid-infrared spectra.

Lab Notes

Colored diamonds
• A quick examination with a spectroscope may confuse yellow cubic zirconia with a yellow or treated yellow diamond. The West Coast Lab examined two kite-shaped step cuts submitted for diamond color origin determination. Observation of their spectra using a desk-model spectroscope revealed an apparent cape spectrum with the 595 nm line that often indicates irradiation and annealing in a yellow diamond. Subsequent tests, however, proved the gems were cubic zirconia. A closer look at the visible absorption spectra revealed slight differences that a quick check might miss.

• Two orange diamonds were examined by the East Coast Lab. The 5.89-ct. round brilliant was Fancy pinkish orange, while the 4.31-ct. emerald cut was Fancy orange. In both cases, however, the orange color was concentrated in the culet, which is commonly seen in diamonds that have been subjected to irradiation and subsequent annealing. This type of treatment was confirmed by their UV-visible spectra; however, infrared spectroscopy (and the presence of heat-related features on the surface of one of the diamonds) gave evidence of high pressure/high temperature treatment. The diamonds apparently had been subjected to multiple treatment processes, which presents a new identification challenge for the laboratory gemologist.

• Three melee-sized bright orange yellow synthetic diamonds were submitted to the West Coast Lab for color origin and identification reports. The diamonds ranged from 0.11 to 0.16 carats. In the DiamondView™, they displayed fluorescence patterns typical of synthetics but were otherwise not easily identified by standard gemological testing. A greater number of small synthetics have been coming through the Laboratory in recent months.

Gem News International
This section features a detailed report on the new source of copper- and manganese-bearing tourmaline from Mozambique that has blue and blue-green colors resembling the Brazilian "Paraíba" variety. The researchers examined 12 samples, providing their gemological properties, and confirmed that the colors were caused by these elements.

Until recently, painite was one of the rarest of all gem minerals, with fewer than 10 crystals known to exist. That situation has changed, however, with the discovery of a number of the crystals in a secondary deposit in Myanmar (Burma). More than 1,000 crystals of the reddish gem have been recovered thus far, though only a small percentage of these were suitable for faceting.

Other items include a look at ornamental blueschist from northern Italy; a rare "phantom" emerald crystal from Colombia's Muzo Mine; a 68.55-ct. grossular garnet from East Africa; green orthoclase feldspar from Vietnam; and an update on tourmaline production from Mt. Mica, Maine (See Loupe story, "Mud, Sweat and Tears," this issue).