Chrysoprase

Chrysoprase is the medium yellowish-green variety of chalcedony. The word chrysoprase comes from the Greek Chrysoprasos: chrys, meaning “golden,” and prasos —or prason —meaning “leek” (the garden herb, similar to, yet much larger than, a spring onion). Chalcedony is a cryptocrystalline (or microcrystalline) variety of quartz. Chrysoprase is just one of dozens of gem chalcedony varieties. But of all the many beautiful gem chalcedonies, chrysoprase is the most highly regarded. This is not necessarily because of its unique qualities, but because it can look like jade (jadeite and nephrite, as well as the comparable serpentine. In fact, one of its more important localities, the Marlborough district in Queensland, Australia, has provided the gem with the commonly known misnomer “Queensland Jade.” Not surprisingly, much of Queensland Jade for the past 40 years has been shipped to and sold in Hong Kong, the jade capital of the world, and today the main production of Marlborough chrysoprase is owned by a Hong Kong firm.

Other localities for chrysoprase now include many other portions of Australia, Russia (Ural Mountains), Zimbabwe, Madagascar, Republic of South Africa, and India. An important chrysoprase locality for the United States is in Tulare County, Calif. Poland is referenced as the “historically important” site.

Chrysoprase has been used as a gem material dating back to at least the days of the Roman Empire, and some say as far back as pre-dynastic Egypt. It has been found in old Greek and Roman tombs, as engraved stones, used as a seal, and carved as intaglio and cameo pieces as well as scarabs.

Chrysoprase can be used as an alternative birthstone for those born in May.

Qualities. Hue, color saturation, and evenness of color are the most important quality marks for chrysoprase. The more pure and saturated the hue, and the more evenly distributed the color, the more valuable the gem will be.

Mostly described as either yellowish-green or “apple green,” the particular balance of yellow and green is a matter of personal taste. It is commonly agreed, however, that the less yellow, the better the hue. This is in keeping with the notion that the more valuable color is the one that approximates jade. As for transparency, as with jade, the best chrysoprase is closer to semitransparent than to the more typical translucent-to-opaque range.

Enhancements and simulants. Other chalcedonies, specifically translucent off-white or gray chalcedony, can be color enhanced—usually by dye—to appear like chrysoprase. Identification is commonly through the use of a Chelsea filter or spectroscope, both of which are used in determining coloring agents. Most dyes use chromium, while most chrysoprase is colored by nickel. Nickel-rich mineral deposits where chrysoprase is located include those found in Brazil and Australia. Rare chromium deposits in southern Africa have produced chrome-colored chrysoprases.

In the past, glass has made for a good substitute when chrysoprase was unavailable. The unusual devitrified glass, a partially crystallized material, sometimes masquerades as chrysoprase in older jewelry. Chrysoprase typically does not have any distinguishing surface characteristics, but this particular glass shows a fernlike surface structure under magnification.

Pricing. There doesn’t seem to be much of a pricing structure for chrysoprase. But like most chalcedonies, price is based on color and on the quality of the design of the gem. Standard cabochons for women’s rings and pendants are sold by the measurement. Carvings by gem artists like Steve Walters, Ramona, Calif.; Glenn Lehrer, Larkspur, Calif.; and Dieter Lorenz, Idar-Oberstein, Germany, are priced according to their artistic value.

As Walters has mentioned in the past, “Chrysoprase, just like black chalcedony, is like working with a blank canvas, only chrysoprase is a little bit more frustrating. The rough has been high-graded many times before it gets to the U.S. gem carvers. So much of the material we have to work with is included, and many times the inclusions don’t show themselves until you’re actually working on it.” (See “Jewel of the Month,” JCK, May 2002, p. 99.)

Walters pointed out that the best is from Marlborough, and it goes to China. The Brazilian material, while very pretty, is included, and working on more difficult rough adds to the price. Says Walters: “We charge for the labor, the wear-and-tear on our carving tools, and the years of experience to do something nice to the gem.”

Care and cleaning. Ultrasonic cleaning for chrysoprase and other chalcedonies shouldn’t be a problem. However, like any quartz or chalcedony, chrysoprase can be scratched, so take care not to let it rub against any other gems or jewelry.

Bench repair and setting. Chrysoprase and its sibling chalcedony varieties are durable (a hardness of 7, a toughness rating of “good”) and can be prong set, bezel set, or set with a combination of prongs and bezels. Most chalcedonies are sensitive to heat, but chrysoprase is even more so, and it easily fades when exposed to temperatures just over 160° F. Remove the stone prior to retipping or sizing.

Recommended reading. For more information, log onto www.nrm.qld.gov.au/mines/fossicking/chrysoprase.html and www.gem.org.au/gallery/chrysoprase.html.

Special thanks to Steve Walters, Ramona, Calif., and Don Olson, Bonsall, Calif.