Search Results

A 9.30 ct oval cut and a 4.12 ct triangular cut of a new type of moonstone from Madagascar featuring an orange flash effect. Photo by Robert Weldon; courtesy of Dudley Blauwet Gems.

New High-Quality Rainbow Moonstone from Madagascar

Jennifer Stone-Sundberg, May 3, 2024

A new type of transparent moonstone seen in Tucson displays a distinct orange flash effect.

Blue amber beads from the Dominican Republic

Color Phenomena of Blue Amber

Yan Liu, Guanghai Shi, and Shen Wang, July 25, 2014

Investigates the presence of fluorescence, rather than iridescence, as the cause of color in blue amber from the Dominican Republic and Indonesia.

Figure 1. Faceted Oregon sunstone crystals (2.75–7.71 ct) representing the variety of colors observed. Photo by Adriana Robinson. Courtesy of the GIA Museum. Gifts of Western Ventures (pear shape), Dust Devil Mining Co. (oval), and John and Laura Ramsey (emerald cut on the far right).

Special Colors and Optical Effects of Oregon Sunstone: Absorption, Scattering, Pleochroism, and Color Zoning

Shiyun Jin, Aaron C. Palke, Nathan D. Renfro, and Ziyin Sun, November 3, 2023

Details the colors and optical effects caused by metallic copper inclusions in this gem-quality feldspar.

Interference figures in faceted alexandrite

Pleochroism and Color Change in Faceted Alexandrite: Influence of Cut and Sample Orientation

Karl Schmetzer, May 15, 2019

Shows how alexandrite’s color and color change are affected by cut and the orientation of table facets.

Pleochroism in Faceted Gems: An Introduction

Richard W. Hughes, October 31, 2014

Describes the phenomenon of pleochroism and its complex effect on the appearance of colored stones.

Trapiche and More...

Duncan Pay, November 6, 2015

Colombia’s unique trapiche emeralds exert a fascination for many gemologists.

The copper inclusions produce a golden chatoyancy.

Cat’s-Eye Paraíba Tourmaline with Copper Inclusions

Yuxiao Li, November 11, 2022

The Tokyo laboratory examines a Paraíba tourmaline with chatoyancy caused by copper inclusions.

Large Cat’s-Eye Emerald from Brazil

Stefanos Karampelas, Lore Kiefert, and Wenxing Xu, July 31, 2015

A translucent Brazilian emerald exhibiting pronounced chatoyancy is examined.

Article

Mixed-Type Cape Diamond

Martha Altobelli and Paul Johnson, September 18, 2014

A natural cape diamond with unusual features is examined in the New York lab.

Top and bottom views of mabe samples from Mayotte.

Mabe Cultivation in Mayotte

Sophie Leblan, Ugo Hennebois, Aurélien Delaunay, Bérengère Meslin Sainte Beuve, Annabelle Herreweghe, Stefanos Karampelas, Maxence Vigier, and Emmanuel Fritsch, November 10, 2021

Laboratoire Français de Gemmologie (LFG) receives several assembled cultured blister samples from Mayotte for gemological characterization.

Types

Topics

Topics

Gemstones

Search Results

Types

Topics

Topics

Gemstones

You Might Also Like

Join Us atConverge

Learn About Education On Campus and Online

Explore GIA Laboratory Promotional Offers

Shop theGIA Store

Join Us at
Converge

Shop the
GIA Store