The Beauty of Natural Green Diamonds
Naturally colored green diamonds are among the most rare and enigmatic of gems, and those with saturated hues—like the stunning examples on our spring issue cover—are highly coveted. Their color origin remains extremely challenging for gemological laboratories to determine.
In our lead paper, Drs. Christopher Breeding, Sally Eaton-Magaña, and James Shigley review these extraordinary gems, identifying four distinct causes of their green colors— radiation damage defects, luminescence from H3 defects, and absorptions by hydrogen and nickel-related defects— and discuss the difficulties of separating these gems from those colored by manmade irradiation treatments. Using data and observations based on thousands of samples from GIA’s research database, the authors offer an unrivaled gemological characterization of these remarkable gems. We’re delighted to present this article, which is the first in a series on colored diamonds by the same authors.
Our second paper, by Xiayang Lin, Peter Heaney, and Jeffrey Post, investigates the cause of iridescence in metamorphic “rainbow” hematite from Brazil. The authors use electron microscopy, atomic force microscopy, and X-ray diffraction to identify the repeating microstructures responsible for the material’s intense iridescence: oriented arrays of spindle-shaped hematite nanocrystals that form diffraction grating.
In our final feature article, pearl specialists Kazuko Saruwatari, Michio Suzuki, Chunhui Zhou, Promlikit Kessraprong, and Nicholas Sturman apply DNA identification techniques to determine mollusk species by sampling tiny amounts of pearl powder. Their study—using akoya pearls from Ehime Prefecture, Japan—was able to amplify genetic material from this powder and successfully match it with the same gene in mantle tissue from the local Pinctada fucata oyster.
Among the standout topics in our spring issue Lab Notes are entries on CVD synthetic diamonds above three carats, a new Kyocera plastic imitation opal, and a real curio: an extraordinary natural blister “pearl” that formed around a pearlfish. Please explore the inner world of gems with our Micro-World column—this issue we feature a type IIa natural diamond with extraordinary etch channels, an opal with agate-like bands, and a pink tourmaline with spodumene inclusions.
In addition to aquamarine from Pakistan’s Shigar Valley and natural freshwater pearls from Texas, our GNI section showcases the 2018 Tucson gem shows. It summarizes market trends from this year’s show and includes entries on leading jewelry designers, gem artists, and materials such as Russian and Namibian demantoid garnet, fine opal, Oregon sunstone, and turquoise from Arkansas.
Congratulations to the winners of our Dr. Edward J. Gübelin Most Valuable Article Award, announced in this issue. We offer a big “thank you” to all of the readers who voted. Don’t forget to take this year’s G&G Challenge, our annual multiple-choice quiz.
Lastly, please join us for the 2018 GIA Symposium, which takes place October 7–9 in Carlsbad, California. We encourage you to register to attend or submit an abstract for an oral or poster presentation at symposium.gia.edu.
