Natural Blue and Black Diamonds, a Byzantine Garnet Intaglio, Yogo Sapphires, and “Kasumiga Pearls”
Characterization of diamond—both natural and synthetic—is a common thread for three of our Summer issue’s six papers. This large issue also contains a synthetic diamond chart and our new regular feature “Diamonds from the Deep,” which aims to demonstrate the value of the natural gem to science and our understanding of the earth’s depths.
However, we have much more besides diamond to offer, including Byzantine garnets, Yogo sapphires—which grace the cover—and cultured freshwater pearls from Japan’s Lake Kasumigaura.
First, lead authors Sally Eaton-Magaña, Christopher M. Breeding, and James E. Shigley review the science of naturally colored blue diamonds, which are among nature’s rarest and most valuable gems. This is the second in their series of papers focused on natural-color diamonds. Although boron impurities are top of mind for most people, the authors detail other causes of blue color in diamond, including radiation-induced defects and complex defects involving hydrogen.
Our second paper, by Karen V. Smit, Elina Myagkaya, Stephanie Persaud, and Wuyi Wang, turns the focus to Fancy Dark brown-black diamonds from Zimbabwe’s Marange deposits. Their dark appearance is caused by a combination of tiny, methane-associated graphite inclusions, graphite needles, and brown radiation stains resulting from the diamonds’ billion-year contact with radioactive minerals in the Umkondo conglomerate.
In our third paper, H. Albert Gilg, Karl Schmetzer, and Ulrich Schüssler tell a fascinating story. Using contemporary nondestructive analytical methods, they trace a Byzantine garnet intaglio back to its geographical source in Telangana State, India. The study reveals much about the ancient trading of Indian garnet.
Our fourth article, by Ahmadjan Abduriyim, profiles Japanese freshwater pearls, first cultivated in Lake Biwa, and then in Lake Kasumigaura, where most farms relocated in 1962. Although the production is limited, “Kasumiga pearls” are very attractive, displaying a variety of hues and very good luster.
Sapphires from Montana’s Yogo Gulch are renowned for their vibrant untreated blue color and high clarity. In our fifth article, Nathan D. Renfro, Aaron C. Palke, and Richard B. Berg offer a complete gemological characterization of these unique American gemstones.
Next, Sally Eaton-Magaña and Christopher M. Breeding present a new chart on the growth and characteristics of HPHT and CVD synthetic diamonds, including information on recent advances in technology that enable production of larger, higher-quality synthetics and colorless melee.
I’d also like to draw your attention to our three regular sections. Lab Notes includes entries on advances in the size and quality of synthetic diamonds. Gem News International has something for everyone: a green-blue Maxixe-type beryl, the trace element characteristics of “golden sheen” sapphire, and Ethiopian color-change garnets. G&G Micro-World includes a mushroom preserved in copal, microlite crystals in topaz, and a wurtzite phantom in quartz. This issue also presents a new regular column by Karen V. Smit and Steven B. Shirey on the value of natural diamond to science. In their inaugural entry, the authors examine how diamonds help researchers solve the enigma of water’s presence in the earth’s depths.
Finally, we’d like to remind everyone that we’re fast approaching the last chance to register for the GIA Symposium, so please go to symposium.gia.edu if you haven’t already.
Enjoy our summer edition!
