Photos: Robert Weldon/GIA. Courtesy: William Larson. | Chameleon of the Gem World | Alexandrite, one of June's birthstones, is sometimes described as "emerald by day, ruby by night." This is because it can change from a cool greenish color under fluorescent light to a warm reddish color under incandescent light, although alexandrite from different localities can display different hues. Of all the gems with a color-change variety, which include garnet and sapphire, alexandrite is the most sought after.
What causes an alexandrite's color change? It occurs when the gem transmits both green and red light equally, but absorbs light in the middle of the visible spectrum. Since fluorescent light is richer in blue and green wavelengths and incandescent light is richer in red wavelengths, the light source affects what color the gemstone appears to be. Want to learn more about this June birthstone? | Photo: Diego Sanchez/GIA. | A Salty (and Radioactive) Diamond | As the popularity of rare green diamonds increases so does the demand for artificially irradiated green diamonds. The GIA laboratory was recently sent a 2.42 carat green diamond for examination. Microscopic analysis revealed telltale green mottled and shallow radiation stains over large areas of the stone, causing its green bodycolor. These radiation stains were produced by exposing a cut and polished diamond to radioactive salts for an extended period. In the early 1900s, it was discovered that radioactive salts (such as radium) could be used to treat diamonds. However, this method is not often used anymore, as it may produce dangerously radioactive diamonds. Today, most artificially irradiated diamonds are treated with a low-energy electron beam. Want to discover more interesting details about this diamond? | Photo: C. Kamemakanon. Courtesy: American-Thai Trading. | Enstatite is a pyroxene mineral with a Mohs hardness of 5-6. While common as a mineral, it is unusual to see enstatite in gem quality and it is considered a collector's gemstone. It was first documented in the mid-1800s and given its name after the Greek word for "resistor" due to its resistance to high temperatures. It is often found in volcanic rock and sometimes found in meteorites.
The specimens seen here are colored by iron and vanadium with a trace of chromium. The four-rayed asterism phenomenon is caused by light reflecting off two intersecting sets of fine needle-like rutile inclusions. Want to explore more of this unusual gem? | We hope our gem knowledge inspires you to rock on. #knowledgerocks | |
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