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Alexandrite

Green in sunlight. Red in lamplight. Color-changing alexandrite is nature’s magic trick.

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Chrysoberyl Variety

Alexandrite is the color-change variety of the mineral chrysoberyl.

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Green by Day

Alexandrite is bluish green in daylight or fluorescent light.

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Red by Night

Alexandrite is purplish red in incandescent light or candlelight.

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Star-shaped Twin

This alexandrite specimen is made up of three interpenetrant crystals.

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Brazilian Gem

Brazil is one of the most important alexandrite sources.

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Re-entrant Angle

Notches marking the edge of each crystal are called re-entrant angles.

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Tools

Research

Figure 11. Double-strand natural saltwater pearl necklace. Photo by Robert Weldon; courtesy of Karmshil Enterprise. Alexandrite exposed to incandescent illumination (left, red) and daylight-equivalent illumination (right, green). Photos by Robert Weldon; courtesy of GIA’s Dr. Edward J. Gübelin collection, no. 33805. Ring containing a CVD-grown diamond. Photo by Johnny Leung.
Classification of Gem Materials Using Machine Learning

Explores the application of several machine learning models to complement traditional gem classification approaches.

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Figure 1. This 0.73 ct octagonal step cut was composed of chrysoberyl and alexandrite. The alexandrite portion showed a color change from blue-green in fluorescent light to red-purple in incandescent light. Photos by Shunsuke Nagai.
Bicolor Chrysoberyl with Chrysoberyl and Alexandrite Zones

The Tokyo laboratory reports on a submitted stone composed of both chrysoberyl and alexandrite.

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An octahedral fluorite crystal in a 1.25 ct Brazilian alexandrite. Photomicrograph by Hikaru Sato; field of view 2.37 mm.
Fluorite in Brazilian Alexandrite

An octahedral fluorite crystal is observed in Brazilian alexandrite.

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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

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

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Figure 1. Top: Negative crystal in an alexandrite containing a fluid and crystals at room temperature. Bottom: Below 31.2°C, multiple gas bubbles appear. Photomicrographs by Jamie Price; field of view 1.99 mm.
Three-Phase Inclusion in Alexandrite

Examination of alexandrite reveals three phases of matter within a single inclusion suite.

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Gemstone classics from sources old and new
The Geographic Origin Dilemma

An overview of the geographic origin complexities facing the gem and jewelry industry today.

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A group of rings featuring alexandrite from Brazil
Geographic Origin Determination of Alexandrite

The geographic source of this rare color-change gem has a significant impact on value. Trace element chemistry profiles allow GIA to accurately determine origin for alexandrite from several countries.

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Field gemologists sort through gem gravel in Myanmar
Field Gemology: Building a Research Collection and Understanding the Development of Gem Deposits

With more than 90 field expeditions on six continents since 2008, GIA has accumulated over 22,000 colored stone reference samples. This extensive collection of colored stones with known origins supports GIA’s research on geographic origin determination.

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A large group of people outside on GIA’s Carlsbad, California  campus.
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Guardians of Trust: GIA’s Innovative Research, Instruments and Services

GIA’s services and instruments have grown in importance and impact as new gem treatments and laboratory-grown gems enter the market.

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Interference figures in faceted alexandrite
Pleochroism and Color Change in Faceted Alexandrite: Influence of Cut and Sample Orientation

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

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