Gemstone Alert: Gemlab Identifies Faked Emeralds
Thomas Hainschwang with Gemlab Gemological Laboratory announced that he recently examined and tested three(3) Emeralds that were purchased in India. The stones were reportedly guaranteed by the Seller to be completely natural and untreated Emeralds. The stones were translucent, green in color as one would expect, and full of fibrous inclusions. When examined under a microscope Hainschwang reported that these stones were not full of fibrous inclusions but, instead, actually had a fibrous structure! It was also noted that the green coloring was concentrated within this fibrous structure. This of course indicates that the material is dyed and not an Emerald.
Next the emeralds were tested via Fourier-transform infrared spectroscopy. They were first tested in reflectance mode which indicated the stones were Al2SiO5, which is the chemical composition of Sillimanite. Afterward they tested the same samples in absorbance mode which showed considerable amounts of oil.
Sillimanite has been used in the past to fake rubies as well by dying it red ( http://gemologyproject.com/wiki/index.php?title=Sillimanite ). It is frequently used to fake other stones due to its fibrous structure which lends itself to easily accept dyes which can reach deep into the material. Sillimanite is also known as Fibrolite.
Sillimanite dyed to resemble Emeralds. Photos by T. Hainschwang.
As Reported by G&G eBrief November 4, 2009 Volume 1, No. 2.