Gem Art of the Taj Mahal, Fancy White and Black Diamonds, and Unique Inclusions in Thai Corundum
Welcome to the Fall 2019 issue of G&G! Inside you’ll find eight articles on a variety of gemological topics, plus dozens of brief reports and discoveries from contributors around the world.
Our lead article delves into the gem art of the iconic Taj Mahal. Dona Dirlam and co-authors examine the intricate gem inlay that graces this architectural treasure, as well as the gem connoisseurship of the Mughal dynasty and how it influenced global gem commerce in the seventeenth century.
In the second article, Sally Eaton-Magaña and Christopher M. Breeding continue their series of colored diamond characterization studies with an in-depth look at Fancy white and Fancy black diamonds. Their systematic study, based on GIA’s data for approximately 500 Fancy white and 1,200 Fancy black diamonds, is the first of its kind for these uncommon diamonds.
Next, Yang Hu and Ren Lu offer a gemological, spectroscopic, and chemical analysis of emeralds from Malipo County in Yunnan Province of southwestern China. Among notable deposits worldwide, Malipo emerald has a unique chemical composition: a combination of high vanadium, low chromium, and moderate iron, as well as high lithium and cesium concentrations.
Supparat Promwongnan and Chakkaphan Sutthirat use Raman spectroscopy and electron probe micro-analysis to identify mineral inclusions in alluvial corundum from the Bo Welu gem deposit in Thailand’s Chanthaburi Province. Several of the inclusions they identify are reported for the first time in Thai corundum.
Next are a pair of studies on organic gem materials. Yamei Wang and co-authors explore hydrothermally treated “beeswax” amber, offering a series of comprehensive tests to identify this product and separate it from untreated material. Kannika Kanjanachatree and co-authors follow the operations at a pearl farm in Phuket, Thailand, to determine the effects of mollusk size on growth and color of half-cultured pearls from Pteria penguin.
The issue rounds out with two brief but informative studies. Wenqing Huang and co-authors investigate a hydrogen-rich faceted green diamond color-treated by a complex multi-step process that has not previously been reported in the gemological literature. Last, Hanyue Xu and Xiaoyan Yu analyze a new rhodochrosite imitation composed of pressed gibbsite and calcite powder with a granular structure.
Highlights from the Lab Notes section include a faceted diamond with a star-shaped cloud inclusion, new resin imitations of ivory, and cobalt-coated sapphire. Micro-World once again offers up a variety of beautiful and unusual scenes from the inner world of gemstones. Among the many Gem News International reports are a new source of Nigerian aquamarine, black non-nacreous pearl imitations made of beads cut from shell, and the new mineral johnkoivulaite. This member of the beryl family is named in recognition of distinguished researcher and longtime G&G contributor John Koivula. Congratulations to John for this exceptional honor—well deserved!
