If you love magic, especially the magic of science, you’ll love Alexandrite, the color-change gem. Outside in daylight, it is a cool bluish mossy green. Inside in lamplight, it is a red gem, with a warm raspberry tone. You can watch it flick back and forth by switching from fluorescent to incandescent light.
Alexandrite is a gem variety of the mineral Chrysoberyl. It was discovered in 1830 in Czarist Russia. Since the old Russian imperial colors are red and green, it was named after Czar Alexander II on the occasion of his coming of age.
Today, fine Alexandrite is most often found in period jewelry since newly-mined gems are extremely rare. You’ll see fine gems offered at auction with impressive estimates. The original source in Russia’s Ural Mountains has long since closed after producing for only a few decades and only a few gemstones can be found on the market today. Material with a certificate of Russian origin is still particularly valued by the trade. Some Alexandrite is found in Sri Lanka, Zimbabwe, Tanzania, Madagascar and Brazil, but very little shows a dramatic color change. For many years, Alexandrite was almost impossible to find because there was so little available.
Then in 1987, a new find of Alexandrite was made in Brazil at a locality called Hematita. The Hematita Alexandrite shows a striking and attractive color change from raspberry red to bluish green. Although Alexandrite remains extremely rare and expensive, the production of a limited amount of new material means a new generation of jewelers and collectors have been exposed to this beautiful gemstone, creating an upsurge in popularity and demand.
Alexandrite is also known as the alternative Birthstone to Pearl for June.
Why does Alexandrite appear to change color in sunlight and artificial light?
Alexandrite is a trichroic gemstone which absorbs and reflects light differently in each of its three optical directions. Spectroscopic analysis reveals a different absorption spectrum for each of the three optical directions. The differences in absorptions cause different colors to be seen when viewed from different directions in relation to the crystal structure. However, it is not the trichroism that is responsible for the remarkable color change. The color change phenomena is a result of the presence of chromium +3 ions and the way they absorb and reflect light. In Rubies the chromium absorption band is around 550 nanometers and in Emeralds, the band is around 600nm. In Alexandrite, where the band is at 580nm and right between ruby red and green emerald, the stone is balanced between them. Daylight contains high proportions of blue and green light and incandescent lighting contains a higher balance of red light. When the light is balanced (daylight), the stone is green but when the light source is reddish (incandescent), the stone appears red.
Human vision is more sensitive to green light. Alexandrite reflects both green and red light. In daylight, a greater proportion of green light is reflected so we see green. Conversely, under incandescent light more red light is reflected so we see red.
- CATEGORY Gems - About