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This 0.69 ct alexandrite showed a stellate structure due to cyclic crystal twinning and pleochroism, producing a kaleidoscope effect when rotated. These photomicrographs were taken with a single polarizer placed above the stone and a white diffuser below the stone to highlight the color. Photomicrographs by Makoto Miura; field of view 9.80 mm.

“Kaleidoscope” in Alexandrite

Makoto Miura, January 26, 2024

Pleochroic colors caused by cyclic twinning produce a kaleidoscope effect in alexandrite.

Rough diamond crystals exhibiting both pink and colorless sections.

Bicolor Rough Diamond Crystals

Sally Eaton-Magaña, Paul Johnson, Ellen Barrie, and Michaela Hariňová, July 9, 2021

Two Australian rough diamonds demonstrate both pink and colorless sections in the same crystal.

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.

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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.

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