Researchers invent a way to identify blue diamonds

The method is called as 'diamond fingerprinting method'

The eerie phosphorescence displayed by a rare form of blue diamond can be used as an easy, cheap, and nondestructive way to identify individual gemstones and to distinguish natural blue diamonds from synthetic ones, analyses suggest.

A research team has found a way to identify a rare blue diamond. Their method is termed as the 'diamond fingerprinting method'. The team includes a Penn State University minerologist, Peter J. Heaney, professor of geosciences, and researchers like Jeffrey E. Post, Smithsonian's curator of gems and minerals, and Sally Eaton-Magana from the Naval Research Laboratory.

found at diamondworld.net 1/17/2008 

The team conducted its experiments at the Smithsonian's National Museum of Natural History in Washington on the Hope Diamond. 

Blue diamonds are known to react with ultraviolet rays. 

They exposed the hope Diamond to the rays and noted that the diamond glowed with a reddish-orange phosphorescence colour for five minutes, and the emitted rays were of varying wavelengths, which became a marker for a blue diamond.

  Another way to determine was by noting the time span it takes for the intensity of the phosphorescence to reduce by half. The study says that a combination of the two provides a unique fingerprint, but further tests are necessary to confirm the findings, as only the Hope Diamond and few other blue diamonds react with the reddish-orange phosphorescence when exposed to ultraviolet light, while most remain blue in colour. 

The conclusions of the experiments have been published in Geology. What was certain through the experiments was that each blue diamond displayed a unique ratio of wavelengths of red and blue light and half-life of its phosphorescence.

Researchers also tested two synthetic blue diamonds and a treated diamond, which produced different results from natural diamonds, drawing the conclusion that the method for synthetics is different than that for naturals. 

According to Dr. Heaney, the team’s identification method can make people aware of the conflict diamonds and help them make better choices in their purchases. The method can also be employed for finding diamonds produced from larger diamonds.

Hued Afterglow: Fingerprinting diamonds via phosphorescence

By Sid Perkins found at sciencenews.org

The eerie phosphorescence displayed by a rare form of blue diamond can be used as an easy, cheap, and nondestructive way to identify individual gemstones and to distinguish natural blue diamonds from synthetic ones, analyses suggest.

BURNING BRIGHT. Aspects of the phosphorescence of natural blue diamonds, such as the famed Hope Diamond (seen in visible light, left, and glowing in the dark after exposure to light, right) can serve as virtual fingerprints for the gemstones.
photo: C. Clark/Smithsonian Institution; J. Hatleberg

Phosphorescence, a "glow-in-the-dark" process in which energy previously absorbed by a substance is released slowly in the form of light, is common in a certain type of blue diamond. After exposure to light, these type IIb diamonds, which have boron- and nitrogen-containing impurities, softly glow in colors ranging from blue through pink to fiery red, says Sally Eaton-Magaña, a chemical engineer at the Gemological Institute of America in Carlsbad, Calif. The orange-red glow from the 45.52-carat Hope Diamond, a type IIb gemstone on display at the Smithsonian Institution in Washington, D.C., is visible for as long as a minute after the lights go out.

Although millions of visitors to the Smithsonian's National Museum of Natural History see the Hope Diamond each year, the gem has received remarkably little scientific attention. While a set of 239 colored diamonds known as the Aurora Heart Collection was on loan to the museum in 2005, Eaton-Magaña and her colleagues studied the set's type IIb diamonds as well as the Hope Diamond and the museum's 30.62-carat Blue Heart Diamond. They also studied the blue diamonds in the Aurora Butterfly Collection in New York City. In all, the researchers studied 67 natural blue diamonds, 3 synthetic ones, and a gray diamond that other researchers had turned blue via treatments at high temperature and high pressure. In some of their tests, the scientists shone a high-intensity ultraviolet light on each gemstone for 20 seconds and then measured its phosphorescence at various wavelengths.

Reddish phosphorescence in diamonds was thought to be rare, says Eaton-Magaña. However, the tests showed that all natural type IIb diamonds glow for several seconds at two visible wavelengths—a 500-nanometer, greenish-blue light and a 660-nm reddish one. The relative strengths of the phosphorescence at the two wavelengths dictate the hue of a stone's overall glow. Differences in the peak intensities of those emissions and the rates at which they wane provide a virtual fingerprint for each stone, the researchers report in the January Geology.

Neither the synthetic stones nor the color-enhanced gray gemstone glowed at the 660-nm wavelength. The new technique's ability to distinguish between artificial diamonds and the true blue gems "solves one of the big problems in diamond markets," says Stephen E. Haggerty, a geologist at Florida International University in Miami.

Tests on the Hope Diamond suggest that variations in phosphorescence from one part of a large gem to another are negligible, says Eaton-Magaña. Scientists would therefore still be able to identify the pieces of a large diamond if it were stolen and cut into smaller stones.