Professional Jeweler Archive: Natural Alternative

February 2000

Gemstones & Pearls: Gemology


Natural Alternative

Iolite steps in where tanzanite dropped off


For jewelers and designers who can’t find tanzanite as supply continues to dwindle, iolite is emerging as a beautiful, natural alternative.

Like tanzanite, iolite comes in attractive blues and violets. Unlike tanzanite, iolite is completely unenhanced. It’s mined in remote localities in India, Africa, Madagascar, British Columbia, Canada and Brazil and is considered rare in its best qualities, especially when it’s over 5 carats.

Iolite (also known as cordierite) has lurked behind the scenes for the past decade, mostly attracting collectors, and has been found mainly as a byproduct in the search for other gemstones.

The gem can be a challenge to cut because it’s strongly dichroic. It appears dingy brown on one axis and violet or blue on the other. In addition, stress related to the cutting process can cause it to cleave easily in one direction; for the same reason, iolite requires an expert gem setter (so does tanzanite, because of its relative softness).

Though gemologists place iolite on the list of important gemstones, a market hasn’t materialized for it yet. However, the dwindling of tanzanite opens the door. “Iolite is back on track,” says Stuart Robertson of Gemworld International Inc., Chicago, IL, a company that publishes a pricing guide.

Demand is climbing for 2-5-ct. iolite, says Bear Williams of Bear Essentials, a gem dealer in Jefferson City, MO. He says improved cutting and better availability will contribute to the growing demand. The price is attractive also. “Fine 2-5-ct. iolite sells at $40-60 per carat wholesale,” says Robertson. For comparison, tanzanite in similar sizes is over $500 per carat.

  • Bear Essentials, Jefferson City, MO; (573) 635-0618.
  • Gemworld International Inc., Northbrook, IL; (847) 564-0557.

– by Robert Weldon, G.G.

Demand for iolite is growing because of its attractive color, affordable price and absence of treatment. Gems are courtesy of Bear Essentials, Jefferson City, MO.
Fine tanzanites – such as these fashioned by Stephen Avery – are over $500 per carat because of short supply. Stephen Avery, Lakewood, CO; (303) 985-4005.

Iolite
Tanzanite
1,542-1,551
Refractive Index
1,691-1,700
2.61
Specific Gravity
3.35
7-7.5
Hardness
6-7
Fair (cleavage)
Toughness
Fair to Poor
Strong Violet/ Yellow
Pleochroism
Strong Blue/Purplish,
Red/Greenish Yellow,
or Blue/Gray
None
Enhancements
Heating


Copyright © 2001 by Bond Communications