Laboratory-Grown Gems

>> Questions &&

  1. Synthetic tanzanite is also known as:
    A. Blue moissanite
    B. Blue glass
    C. Synthetic purple/blue sapphire
    D. None of the above—there’s no such thing as synthetic tanzanite

  2. Fordite, a.k.a. Dearborn agate, returned to Tucson this year. What is this “industrial” gem material?
    A. Industrial diamond
    B. Synthetic industrial diamond
    C. Automotive paint
    D. Ground agate, dyed and recon- stituted as gem-quality cabochons

  3. Moissanite is sold on TV as simply “moissanite.” What is “synthetic moissanite”?
    A. The exact same gem material as moissanite
    B. Heat-treated moissanite
    C. High-pressure/high-temperature treated moissanite
    D. Fracture-filled moissanite
    Bonus Essay Question What is the chemical makeup of “synthetic moissanite,” and why is this so important outside the gem industry?

  4. Are there commercially available synthetic colorless and near-colorless gem-quality diamonds?
    A. Yes
    B. No
    C. Yes and no
    D. Maybe, maybe not

  5. Which synthetic is most likely to be used in high-school and college class rings?
    A. Synthetic corundum
    B. Synthetic spinel
    C. Synthetic spinel triplets
    D. All of the above

  6. What is the most likely synthetic to be found in jewelry labeled “alexandrite”?
    A. Change-of-color synthetic spinel
    B. Change-of-color synthetic sapphire
    C. Synthetic alexandrite
    D. Change-of-color synthetic tanzanite


  1. D. There is no synthetic tanzanite, i.e. synthetic purple-blue zoisite, yet. The closest synthetic substitute for tanzanite is still synthetic forsterite. Refractive index is similar to peridot, approximately 1.65–1.67 (slightly lower than tanzanite’s 1.69–1.70), since they are in the same mineral group.

  2. C. Back in the ’50s, ’60s, and ’70s, during the heyday of the Detroit automobile, the walls of paint stalls in auto factories became coated with layer upon layer of automotive paint. Periodically, the walls would be stripped, creating striped paint blocks just waiting for someone to trim, cut, and polish them into gem cabochons.

  3. A. Most retailers, and this includes television retailers, leave off the word “synthetic.” Like cubic zirconia, which is also a synthetic, there are natural counterparts. However, they are simply too small and rare to compete with the synthetic material.
    Bonus Essay Question: Synthetic moissanite is silicon carbide (SiC), which is useful in many electronics applications. When grown in crystals large enough to produce gemstones, this material also can be used for power transistors and semiconductors as well as ultra-thin and high-intensity LEDs. Charles and Colvard, North Carolina distributor of synthetic moissanite gems, receives its supply of moissanite from Cree Research, also based in North Carolina.

  4. C. It’s still too expensive to create colorless and near-colorless HPHT synthetic gem-quality diamonds commercially. However, with the advent of CVD, chemical vapor deposition, near colorless synthetic gem-quality diamonds are now being produced. These are type IIa, which can then be HPHT processed to make them colorless. The synthetic gem-quality diamond industry is rapidly growing.

  5. D. “The common simulated birthstones fall into three categories,” notes Sue Adams, U.S. representative for Stephan, a cutting firm in Idar-Oberstein, Germany, that’s the major supplier of stones for high-school, college, and championship rings. Synthetic corundum: used to simulate garnet (January), alexandrite (June), ruby (July), pink tourmaline (October), and golden topaz or citrine (November). Synthetic spinel: simulates aquamarine (March), diamond (April), peridot (August), blue sapphire (September), and blue zircon (December). Synthetic spinel triplets (spinel top and bottom with color in between): simulates amethyst (February), emerald (May), and topaz (November).

  6. B. While there are a number of very fine quality synthetic alexandrites, the stone most often found labeled “alexandrite” is change-of-color synthetic sapphire. You can tell a synthetic alexandrite-like sapphire by its colors, a teal to blue green in daylight, and dark grayish/bluish to raspberry-purple in incandescent light.