How can I spot the difference between a natural and a synthetic alexandrite?
Natural alexandrite are available in a complete range of colors from brownish to bluish green in daylight to pink, purple, red or brownish red under incandescent light. Compared to natural stones, most synthetic alexandrite are somewhat more blue under fluorescent light and strongly red under incandescent light. In recent years, a synthetic (“cultured”) alexandrite jewelry company has developed a collection of stones which change from turquoise blue tone to tanzanite amethyst purple. Large clean and inexpensive stones offered as natural alexandrite are most probably synthetic or not alexandrite at all. Gemologists study the inclusions to distinguish between natural and synthetic alexandrite, as is the common practice with all natural gems. Synthetic stones may also have a lower refractive index and show more fluorescence than natural stones. Natural alexandrite should be purchased from reputable dealers and expensive stones should also be tested and certified by a well established gem lab, such as EGL.