Alexandrite Buying and the Four Cs
The IGS alexandrite value listing has price guidelines for faceted alexandrite at top, medium, and slight color changes, as well as for cabbed plain and cat’s eye alexandrite with strong color change.
Color Change in Alexandrite
By day, alexandrite should be emerald green to peacock blue. By night, a ruby red or amethyst hue. The intensity of this color change is the most important factor in alexandrite price. Still, intense and complete color changes occur rarely in this stone. Most alexandrites appear muddied in one type of lighting. Thus, the most prized stones undergo a complete shift from lovely green to luscious red. For example, watch the transition of this platinum ring with alexandrite, green sapphires, and diamond accents.
This alexandrite starts green in daylight, then shifts to a deep red in incandescent light. Video © J. Grahl Design. Used with permission.
Some gemological laboratories quantify this shift by a percentage. A 100% change means that the entire stone undergoes color shift. Most high-quality alexandrites exhibit 85-95% change, meaning that some facets don’t change color. However, these results are difficult to reproduce because of the lack of standards in lighting and…