Have a Parti with Bicolor and Particolor Gemstones
Particolored gemstones are a special gift of the gem world. These are gemstones, such as watermelon and bicolored tourmaline, and ametrines, that are not one but two or more colors. They almost always get a second look.
ABOVE: These 30% pinkish, 70% light yellow green bicolored tourmalines are a domestic product from San Diego County. Photo Mia Dixon, courtesy Pala International.
Bicolor Gemstones: Ametrine
One of the most common bicolored stones you’ll find is ametrine. These stones show the lavender to purple shades of amethyst on one end and the golden or honey color of citrine on the other. This is possible, of course, because both amethyst and citrine are quartz, and the color of each is caused by chemical impurities in the mineral. As a quartz crystal grows in the Earth, the chemical content of the solution surrounding it can change. As it does, so does the color of the quartz. Often this creates a variety of shades of purple or yellow, but sometimes, the crystal shares space with both colors. Ametrines come primarily from Brazil.
Bicolor Tourmaline Gemstones
Another gemstone that frequently exhibits two colors at once—and in fact is known for it—is tourmaline. If you haven’t filled your yummy gemstones quotient for the day, you’re about to.
Tourmalines are actually a group of minerals with the same crystal structure but a complex and varying chemical composition. In tourmalines, lithium, aluminum, iron, magnesium and calcium often substitute for each other in a basic chemical formula. Most green and pink tourmalines include lithium and aluminum in their composition. This variety is called elbaite, named after the island of Elba, Italy, where Napoleon was once held prisoner and where pink crystals of tourmaline were once found. (I don’t know if this question will ever be part of Trivial Pursuit, but if it does crop up, you’ll be ready.)
Naturally, this wild roulette wheel of chemical possibilities can lead to gorgeous blends of color. Look at the bicolored tourmalines from San Diego County or the magnificent reddish/yellow green bicolor set in an 18k gold pendant.
Hello? May I have your attention back? Because there is more.
Particolored Gemstones: Watermelon Tourmaline and Liddicoatite
One of the most fascinating particolored gemstones, watermelon tourmaline brings to mind the halcyon days of youthful summers. While most multicolored tourmaline crystals change color from one end to the other, watermelon tourmaline is colored from the center out. Like its namesake, it has a pink to red center and a surrounding “rind” of green. (Well, most of the time.) They are cut into slices to show off this effect.
In 1977, a variety of elbaite (with calcium, lithium, and aluminum in its structure) was described and named Liddicoatite, in honor of Richard T. Liddicoat, long-time president of the Gemological Institute of America (GIA). Not only can Liddicoatite have the pink to green concentric rings of watermelon (it doesn’t always come this way), it often contains an area of triangular color zoning that is unique.
Cut into thin slices to show off the special color zoning (rather than faceted or cabbed), both elbaite watermelon tourmaline and Liddicoatite make stunning centerpieces in jewelry. Slices cut from the same crystal may be similar in color distribution and intensity—and so can be used in earrings and bracelets. But watermelon slices cut from different crystals will rarely match. That means each piece of jewelry made with watermelon tourmaline is unique.
Watermelon tourmaline slices of varying qualities can be found at most gem shows. Prices will depend on the vividness of the colors and the attractiveness of the slice. Liddicoatite slices, however, especially those with clear triangular zoning, are much rarer and much more expensive.
The “parti” nature of these gemstones seem to make them a natural to wear during the light-hearted days of summer. If you’re looking for something different to punch up a particular jewelry design, look no further.
I would like to take this opportunity to thank photographer Mia Dixon and Bill Larson, president of Pala International, as well as The Collector Fine Jewelry, for their extraordinary generosity in supplying images and granting Interweave and Lapidary Journal Jewelry Artist permission to use Mia’s matchless images of Pala’s equally matchless gemstones in these blogs. I am deeply grateful.
Sharon Elaine Thompson is a GG and FGA who has been writing about gemstones and jewelry for Lapidary Journal Jewelry Artist since 1987. She also writes a line of birthstone romance novels under the name Liz Hartley.