Iolite’s most valuable color is a beautiful, saturated violet to blue. Unless inclusions cause phenomena such as aventurescence or chatoyancy, their presence makes iolite less valuable.
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What To Look For
Vivid violet to blue are iolite’s best and most valued colors. It is highly pleochroic, so a cutter must orient the cut of the stone carefully so the best color shows through the gem’s table. Commercial-quality iolite often has a grayish color component.
Generally, eye-clean iolite is most valuable, but the presence of certain types of inclusions in the proper orientation can result in cat’s-eye or aventurescent gems. Phenomenal iolite is rare and coveted by collectors.
Iolite is strongly pleochroic and has one direction of perfect cleavage. These properties can pose challenges during the fashioning process. A skilled cutter can bring out all the beauty iolite has to offer.
Fashioned iolites that weigh from 1 to 10 carats can be found on the market. However, fine faceted iolites over 5 carats are somewhat rare.