Faceted - Top Color: G 5/2 and R or slpR 5/3
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
Alexandrites have two primary value drivers. First, the closer the colors to pure green and red, the higher the value. Second, the more distinct the color change, the higher the value. Alexandrites can exhibit everything from 100% to just 5% color change. Thus, the most valuable gems would have a 100% color shift from pure green to pure red. Blue-greens and purplish or brownish reds hold less value.
Clarity also plays a significant role in grading. As is the case with a majority of gems, most naturally occurring alexandrite isn’t clean, facetable material. Most is best suited for cabbing. However, an alexandrite’s color change has more effect on its value than its clarity. For example, take two alexandrites of equal size. One gem is eye clean, with a 50% greenish blue to brownish red color change. The other is an opaque cabochon with a 100% green to red color change. The opaque cab would be considered more valuable.
Size always affects alexandrite value. You can see this reflected in our Price Guide below. In sizes up to one carat, top-quality natural gems can sell for up to $15,000 per carat. Over one carat, the prices range from $50,000 to $70,000 per carat!
For more detailed value information, see our alexandrite buying guide.
This oval-cut alexandrite has a 100% color change, from a strong blue-green in sunlight to a purple “plum” red in incandescent light. 0.35 cts, 5.1 x 4.2 mm, Russia. For alexandrites, this is a large gem. © Rob Lavinsky, www.iRocks.com. Used with permission.