These fascinating stones change color under different lighting. The star effect can be seen in ruby or any color of sapphire, and it arises from white light reflecting from numerous tiny, oriented needle-like inclusions.īesides fancy sapphire and star corundum, there’s another interesting variety: color-change sapphire. This phenomenon usually appears as a six-ray star pattern across a cabochon-cut stone’s curved surface. Now, contemporary designers arrange fancy sapphires in stunning rainbow suites.Ĭorundum can show a phenomenon called asterism, or the star effect. The colors attracted jewelry designers who wanted to move away from traditional hues of red, blue, and green. The new sources supplemented production from traditional ones like Sri Lanka and Madagascar and increased the availability of yellows, oranges, pinks, and purples. In the 1990s, discoveries in East Africa and Madagascar brought fancy sapphires widespread recognition. Chromium can cause the red color of ruby or the pink of pink sapphire. Only a few hundredths of a percent of iron and titanium can cause the color, and the more iron the corundum contains, the darker the blue. When the trace elements are iron and titanium, the corundum is blue sapphire.
Most corundum contains color-causing trace elements. Colorless sapphires were once popular diamond imitations, and they’ve staged a comeback as accent stones in recent years.īut colorless corundum is rare.
In its purest state, corundum is actually colorless.
However, silicon is a very common element, making natural corundum relatively uncommon. The mineral corundum is composed only of aluminum and oxygen, and it requires a growth environment that’s free of silicon. Red corundum earns the name “ruby.” - Courtesy Omi Gems, Inc. Sapphires come in every color except red. Comprehensive CAD/CAM For Jewelry Certificate
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