the art of fine jewelry

Cupriantourm_(moz)_cts.2.70_p.sh_cts.2.35_sq princ_TRAS_UTLS_05-26-06
Cuprian tourmalines

The Paraíba tourmaline controversy

     It’s been more than a decade since the transcendent neon blues of Brazil’s Paraíba tourmaline first came to market. Like Tanzanite, Paraíba was named for the area in which it was mined, a location that has proved to be unique in all the world. Both of these rare gems have become collectable, and fine gems of size command princely sums. Traces of copper and manganese in the molecular structure are responsible for Paraíba’s stunning color.

     Now the term “Paraíba” is being used to describe other copper-containing tourmalines from Nigeria and Mozambique, and many in the gem world aren’t happy about it. These new gems range in color from shades of robin’s-egg blue to blue-green to green and even violet. They contain the same ingredients as Paraíba tourmaline, but in different concentrations. They’re simply not “Paraíba” in either look or origin, but the sellers of these stones hope the name’s caché will make their stones more salable.

Paraíba tourmaline in Platinum by Alex Sepkus

 Recently the president of the American Gem Trade Association (a gem dealer who just happens to have a large inventory of Mozambique and Nigerian tourmaline), announced that henceforth the AGTA gem lab would certify all copper-bearing tourmalines as “Paraíba”, regardless of origin. He claimed that the AGTA Board had made the decision, but this proved not to be true. In the face of outraged opposition, he took a sudden leave of absence and the AGTA board rescinded the previously announced policy.

     The jury is still out on this issue, but the most recent issue of Gems and Gemology, the quarterly journal of the Gemological Institute of America, reported that probable origin of Paraíba-like tourmaline could now be determined through sophisticated gemological testing (LA-ICP-MS, see article at right). The international Laboratory Manual Harmonization Committee, which includes seven major gemological laboratories, has for now agreed to apply the term “Paraíba” to all blue, bluish-green to greenish blue, green and violet albeit tourmaline that contains copper and manganese, regardless of its origin. But in this country, the FTC forbids using place names to describe gems unless the seller can provide documents to support the claim. Stay tuned–and as always, CAVEAT EMPTOR.

This month’s sources include the article
“Paraíba-type Copper-bearing Tourmaline from Brazil, Nigeria and Mozambique"; and AGTA member bulletins.


LA-ICP-MS: (Laser ablation-inductively coupled plasma-mass spectrometry): a new way to determine origin and detect treatments of gemstones.

     LA-ICP-MS is an analytical technique used to detect the chemical composition of gems. It reveals both additives from gemstone treatments and trace elements that can help determine a gemstone’s probable geographic origin. And that’s a good thing.

     One of the most troublesome developments in gemstone enhancement in recent years has been the large-scale beryllium diffusion treatment of natural sapphire. This treatment can result in color enhancement including complete color change in some cases. (“Rainbow sapphires” are produced by this treatment.)

     Unlike previous diffusion treatments, beryllium diffusion penetrates the entire stone and is impossible to detect without sophisticated testing. Originally only the yellow-orange-purple-pink part of the spectrum was thought to be affected, but we now know that in all probability, nearly all sapphire undergoes this treatment, including classic blue sapphire.

     In LA-ICP-MS testing, a minute amount of the gem sample is vaporized by a high-energy laser beam, and the vaporized material is ionized into a plasma by a high-frequency power generator. Even trace elements in the parts per billion range can be identified. The test leaves a tiny spot on the surface of the sample, and cut gems are generally tested on the bottom of the stone in an area that can easily be repolished.

     LA-ICP-MS allows gemologists to definitively diagnose beryllium diffusion and other treatments. It also makes possible the cataloging of the precise makeup of gems from specific sources, which may ultimately solve the dilemma of place-name designations.

This month's sources include "
Chemical Fingerprinting by LA-ICP-MS” by Abduriyim, Kitawaki, Furuya and Schwarz (Gems and Gemology volume XLII).


Glass filling of highly included natural ruby to significantly enhance clarity

 Once upon a time, a by-product of the routine heat treatment of rubies was the filling of common small surface inclusions with residual flux from the crucibles used in the treatment. Now we are seeing cases where highly imperfect rubies with significant surface fissures have been filled with lead-containing glass that transforms their appearance completely.

     The material used is often very low grade pink, red or purplish Madagascar corundum but glass-filled stones from Tanzania and Myanmar have also been noted. The effectiveness of the treatment is amazing in that it transforms opaque and nearly worthless corundum into material that is transparent enough for use in jewelry. However, ammonia, bleach, and even concentrated lemon juice were found to damage the filler by turning it white at the surface.

     Cavities filled with high-lead glass can be challenging to see under the microscope, but most samples recently examined by the Gemological Institute of America contained gas bubbles and exhibited a blue or orange flash effect at the interface between the natural material and the filler. Glass is significantly softer than ruby, and the filled area may exhibit an inferior polish to that of the natural ruby host.

This month's sources include The Loupe and GIA World News Vol. 15 #3


Buyer Beware Alert
Glass-filled ruby scam in Madison, Wisconsin

In January a woman came to Studio Jewelers with a 6.43 carat ruby that her husband had given her for an important anniversary. She wanted it appraised and set in a custom ring. The ruby was an attractive red color but quite cloudy in appearance due to numerous small inclusions. The customer stated her husband had purchased the ruby from a man he met socially, and had been told it was a natural ruby. He had paid $1,500 cash for it and was told he should insure it “for at least $7,500”. She didn’t identify the seller except to say he traveled a lot, claimed to be in the jewelry business and dabbled in selling gemstones.

Because the range of possible value in a large ruby is so great (depending on whether it’s synthetic, natural, heat treated, color enhanced by beryllium diffusion, or fracture-filled) Hanna sent the stone to the Gemological Institute for certification of origin and treatments. The GIA found the ruby to be extensively glass filled, which put its retail value at well under $300.

This scammer was able to take advantage of this couple’s ignorance of the natural ruby market as well as a common misapprehension about exorbitant margins in the jewelry business, implying that a markup of 500% or more would be normal. The undocumented cash purchase leaves the consumer little recourse.

For more information on this topic, please read the above article on glass-filled rubies