Which stones are substitutes for rubies?

09/05/2008 23:09

Mary Johnson has a doctorate in mineralogy and crystallography and is a former research and development manager at the Gemological Institute of America. Any gemstone questions? Send an e-mail to: NationalJeweler100@yahoo.com. By Mary Johnson

Question: Now that Burmese rubies are being banned by the U.S. government, what other gemstones are good substitutes for rubies?

Answer: Rubies from Myanmar (still commonly called Burma) range widely in price, from top-value, high-clarity stones mined in the Mogok Stone Tract to small, cloudy stones from Mong Hsu, so there is a range of possible substitutes.

Rubies come from numerous other sources around the world, including Vietnam, Madagascar, Thailand, Sri Lanka and the Pamir Mountains border region of Pakistan, Afghanistan and Tajikistan. Many Tanzanian and Kenyan rubies are orangey to brownish, but some are bright red. For the right clients (perhaps scientists or engineers), jewelers might consider high-quality flux (or hydrothermal) synthetic rubies, with proper disclosure, of course.

The best Burmese rubies are not only red from light absorption, but also luminesce red under white light. Most other red gems may have lovely hues, but will not luminesce. These include the very rare taaffeites and red diamonds. Opals and ammolite can achieve bright reds, but do not resemble ruby. Some alexandrites luminesce red, but they appear red-to-purple only in warm lighting.

Spinels come from many of the same deposits as rubies, with some of the best found at the Mogok Stone Tract. Though they lack luminescence, spinels are the best candidates to replace fine rubies, and there are even star red spinels to serve as a substitute for star rubies.

Recent finds of giant crystals at Mahenge in Tanzania have yielded gorgeous clear orangey-pink to red spinels at near-ruby prices. Other excellent spinels come from the Pamir Mountain border countries or from Sri Lanka and Vietnam. Still, synthetic spinels abound, and high-end (flux) synthetics may challenge gemologists.

Another fill-in for rubies are garnets, including rhodolites, Maralambo garnets and chrome pyropes. Since many garnets are dark (or only available in small sizes), you may wish to pavé-set "anthill garnets" or consider cuts with concave facets. Spessartite garnets (and sunstone feldspars, colored by copper) are usually orange, but some are quite reddish.

Eudialytes, helvite and red topaz are other possible ruby substitutes. Gems that are sometimes brownish red include zircon, axinite, monazite and painite.

If pink-to-purple is an acceptable hue modifier, consider red beryl and rubellite tourmaline. Other gems colored by manganese include rhodonite, pyroxmangite and rhodochrosite, but these are too delicate for regular use.

Quartz, included with bright-red rutile, might make a dramatic focal stone for a pendant or brooch. Other included materials are bloodshot iolite and strawberry quartz, but these may be too brownish in color, or cuprite (chalcotrichite) in calcite, which is soft.

Translucent-to-opaque red gems include carnelian, jasper and bloodstone (colored by iron, so usually a "rusty" color); myrickite (chalcedony included by cinnabar) and other materials colored by cinnabar; coral (colored by an organic pigment); and tugtupite (usually pink rather than red).

For gemstone collecting but not wearing, the deepest reds come from sulfides and oxides, including proustite and pyrargyrite (the "ruby silvers," which alter when exposed to air and light), cuprite, cinnabar and "ruby jack" sphalerite.

Editor.s note: This story first appeared in the July 2008 print edition of National Jeweler.