Jeffrey M. Bertman
Graduate Gemologist

Anyone desiring to get the most value out of a gemstone purchase should look into those gemstones that display the optical phenomenon known as “pleochroism.” This term refers to the gemstone’s ability to appear to have different colors (or depth of color), contingent on the angle at which it is viewed. This property owes its presence to doubly refractive crystals in the gemstone’s structure that cause differing absorption of light rays. The optical effect can vary from strong to weak, depending on the gemstone. A good example of a strongly pleochroic gemstone is andalusite, which displays shades of yellow, olive, and reddish brown, based upon on the orientation of the crystal. As for kyanite, it displays different depths of blue.

Pleochroism is absent in gems with no crystal structure, opaque stones, colorless stones and most gems that are translucent rather than transparent. Tanzanite is a strongly pleochroic gem but because tanzanite is always heated to produce the familiar violet blue color, you will rarely see its pleochroism. Diamonds are not pleochric, because they are a singly refractive gemstone. As a couple, select the perfect gemstones to fit your taste for rings, earrings, or pendants at 1402 Hancock Street, Quincy Center. Or reach us at 617-773-3636.