HGMS Presentation ~ “Holography and Gemstones” by Dr. D. Brian Thompson

On 25 October 2016, Dr. D. Brian Thompson will present “Holography and Gemstones”.   Dr. D. Brian Thompson is a Professor of Physics at the University of North Alabama (UNA). He was awarded a Ph.D. in Physics from the University of Kentucky in 1994. He spent five years working at synchrotron facilities in England, Italy, and the U.S., performing synchrotron (x ray) light studies on atoms and small molecules. Joining the UNA Department of Physics and Earth Science in 1999, he began a research program in laser optics. Surrounded by mineral specimens in the department, his attitude toward them has been “if it is transparent, let’s shine laser light through it and see what happens.” He has published an article on laser-excited photoluminescence in emeralds in the Gem-A journal, Journal of Gemology (2014); a follow-up article is currently under review at the GIA journal Gems & Gemology.

According to Dr. Thompson several varieties of gemstones exhibit optical properties arising from light reflections occurring inside the stone, including: play of color seen in opals and the similar labradorescence seen in feldspars such as spectrolite and rainbow moonstone, chatoyancy commonly called “cat’s eye” in many species, asterism that is the star in star sapphires, and adularescence that produces a floating blue cloud in moonstone. Static photography of these optical properties, generally referred to as sheen, presents a problem since the sheen effects change both with perspective and with lighting directions. The photographic image cannot reproduce the changing nature of the sheen exhibited by a gemstone in hand. Holography offers another imaging method that may be able to capture the changeable nature of sheen seen in gemstone. Over the past year, we have built and improved a setup that currently uses three laser colors (red, green, and blue) to create reflection holograms of gemstones. Last spring we were successful in creating a three-color holograms of an opal; to quote an industry expert “it looks as if you can reach through and touch it.” In this talk Dr. Thompson will describe the holographic process, review the opal imaging success, describe the acquisition of other specimens for holography, and provide updates on his current efforts to create holograms from these specimens.

The HGMS meeting starts at 6:30 p.m. Central Time and the presentation begins promptly after.  Hope to see you there!

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