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Figure 1. Iridescent andradite samples (25 ct and 125 ct) from the Lindong area of Inner Mongolia, China. As shown in the left photo, sample G-1 displays iridescence on the (211) plane but not on the (110) plane. Photos by Jiuchang Yang.

A Newly Discovered Iridescent Andradite from Inner Mongolia, China

Jiuchang Yang, Quanli Chen, Fengshun Xu, Yan Li, and Xianyu Liu, November 3, 2023

The first report of iridescent andradite from China.

Figure 2. Rectangular step-cut green beryl from the Volyn pegmatite, 190.00 ct and 28.55 × 39.02 × 21.71 mm, with a rough unpolished table containing etch pits. Faceting and photo by Konstantyn Zalizko.

Etch Pits in Heliodor and Green Beryl from the Volyn Pegmatites, Northwest Ukraine: A Diagnostic Feature

Gerhard Franz, Oleksii A. Vyshnevskyi, Volodymyr M. Khomenko, Peter Lyckberg, and Ulrich Gernert, November 3, 2023

Examines dissolution features of heliodor and green beryl from a Ukrainian pegmatite field and offers criteria to distinguish them from samples found in other localities.

Rare Double-trapiche Emerald

Tao Hsu, March 29, 2013

At the AGTA show, Equatorian Imports showed this contributor two pieces of emerald with a very rare double-trapiche pattern

Zoned Scapolite from India

Gagan Choudhary , March 29, 2013

This contributor encountered parcels of rough and faceted scapolite that appeared strongly zoned to the unaided eye.

DiamondView Imaging of the Pavilion Facets

Pseudo-Synthetic Growth Structure Observed in Natural Diamond

Paul Johnson, March 29, 2013

This stone was a good example of a very rare natural diamond exhibiting synthetic growth characteristics.

Iridescence in iris quartz from Jalgaon, India

Causes of Iridescence in Natural Quartz

Xiayang Lin and Peter J. Heaney, May 8, 2017

Describes the occurrence of iridescence, and the role of differential etching, in quartz crystals from India’s Jalgaon District.

Article

Spring 2023 G&G Available Now

Erica Zaidman, May 23, 2023

An overview of the Spring 2023 Gems & Gemology content.

Figure 1. A 4.56 ct rough diamond with plastic deformation lines, highlighted in the sketch on the right. Deformation has occurred along a set of parallel internal slip planes. The planes appear as thin ridges on the diamond’s surface, exposed by natural dissolution of the surface by fluids (i.e., resorption). In fact, the whole surface has been resorbed into this overall dodecahedroid shape, decorated by elongate hillocks and plastic deformation lines, both fine features representing slight interruptions and imperfections in the diamond crystal lattice. Images by Evan M. Smith.

Plastic Deformation: How and Why Are Most Diamonds Slightly Distorted?

Evan M. Smith, May 23, 2023

A look at plastic deformation, one of the most prevalent features in natural diamond.

Figure 1. Left: This 1.63 ct grayish blue diamond was identified as a CVD synthetic, with its color caused by both the GR1 and SiV<sup>–</sup> centers. Photo by Xiaoyu Zhang. Right: Dark cloud-like non-diamond carbon inclusions. Photomicrograph by Meng Li; field of view 0.25 mm.

Grayish Blue CVD Diamond Colored by GR1 and SiV^–

Wang Yang, Xiaoyu Zhang, and Zhonghua Song, May 23, 2023

Examination of a grayish blue CVD laboratory-grown diamond indicates its color was caused by both the GR1 and SiV^– centers.

Figure 1. These examples of gem minerals that formed in magmatic environments are part of GIA’s Eduard Gübelin Collection. From top to bottom and left to right: 29.96 ct sanidine feldspar from Germany, 53.00 ct peridot from Myanmar, 11.58 ct zircon from Thailand, 20.66 ct topaz from Utah, 2.05 ct sapphire from Thailand, 18.36 ct pyrope garnet from the Czech Republic, 19.55 ct black spinel from Thailand, and 2.50 ct ruby from Thailand. Photos by Robert Weldon.

Gems Formed in Magmatic Rocks

Aaron C. Palke and James E. Shigley, January 25, 2023

This installment of “Colored Stones Unearthed” covers gemstones that formed in magmatic environments and the insights they offer into the evolution of the earth and the geological processes that shaped our world.

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