Rapaport Magazine
Colored Gemstone

The Drusy Mystique

Shimmering drusy is gaining popularity for its range of sparkling colors.

By Sheryl Jones

Daria de Koning

With a sparkle like freshly fallen snow in the sunshine, drusy, a crystal formation on a host rock or mineral, has become a favorite of gemstone enthusiasts. Recently, drusy has begun gaining an even wider audience due to advancements in manufacturing and treatments. Colors that were once considered rare are now more plentiful and better cutting techniques have made shapes more uniform and easier to set in jewelry.

   A cluster of crystals that encrust a wide variety of host rocks or minerals, drusy creates a shimmering effect as light is reflected off the surface. Like most minerals, drusy forms over millions of years. As molten lava is pushed through the surface of the earth, it creates air bubbles. Once these cool, air pockets begin to fill with different minerals. Water enters these cavities and mixes with silica, also known as quartz. Rapid cooling causes the crystals to form.
   Drusy is often seen when it forms inside the cavity of a geode, which is a nodule within lava or ancient volcanic rock. But it can be found on an array of different stones, offering a wide spectrum of colors, shapes and sizes.
   “There is no specific stone that drusy forms on, although it is found in large concentrations of Brazilian quartz and chalcedony. But given the right mineral-rich silica solutions, it can form on a lot of different minerals,” says Mark Lasater, owner of the Clam Shell, a firm specializing in unusual gems and mineral specimens based in Prescott, Arizona.

   Natural drusy can be found on beige, brown, rust, green, blue, gray, white, yellow and purple quartz, chalcedony, agate and jasper. Along with the more familiar stones, drusy can also be found in a variety of harder-to-source minerals, which lend a range of distinctive colors. These include uvarovite, an intense green garnet, black garnet and rainbow pyrite found in Russia, and pink cobalto calcite from the Congo, which ranges in color from a pale pink to hot magenta. Even more difficult to find is psilomelane, the only other natural black color besides garnet.
   Drusy can form on a combination of chrysocolla and malachite, producing spectacular alternating bands of green and blue that range from pale to hot aqua and dark blue to sea foam green or deep emerald green. Judy Kiriazis, owner of Heart of Stone Studio, a web-based company that carries an extensive line of drusy material, points out that the rarest drusy is kammererite, which is the color of grape juice and found in Turkey.
   There are two different drusy crystal structures that affect its color on a host rock. “Some crystals are clear and the color is in the matrix of the host stone. For instance, if you look at the surface of cobalto calcite drusy, which is an intense pink, the crystals on top are clear, so the colored sparkle comes from the rock. Sometimes, the crystals grow in the color of the host stone, as in the uvarovite drusy, an intense green garnet with green colored crystals on top,” says Kiriazis. The sizes of the crystals can vary as well from stone to stone, which affects the intensity of the color tone.
   These factors make each drusy stone special because of the way the crystals illuminate the color of the stone. They can transform a seemingly inexpensive opaque stone into a fascinating gem resplendent with color, depth and scintillation. Mickey Wilcox, jewelry designer and co-owner of Mickey Lynn, an online store, started working with the material in 2008 because “the crystals make the stones mesmerizing and every stone is completely different.”

   Working with one-of-a-kind stones can be challenging for a designer or manufacturer when making pairs of earrings or filling reorders. Organic shapes not cut with exact measurements are not always easy to match.
   “In the late 1980s and early 1990s, people were very interested in drusy, but there wasn’t a cost-effective way to coat stones to enhance the sparkle and color and it was difficult to set,” says Kiriazis. However, innovative treatments and cutting techniques have enhanced drusy’s appeal.
   “Greg Genovese, a stonecutter well known in the industry for his work with drusy material for over 30 years, is credited with pioneering titanium coating. It changes the color to vivid blue, green, purple and iridescent shades,” explains Lasater. The process is known as chemical vapor deposition (CVD) in which vaporized titanium is mixed with oxygen and then placed on the drusy. “Some of these coatings are so thin, they can be compared to a ‘breath on a window’ but are very hard and durable if treated with care,” he adds. Drusy can also be treated with silicone oxide to produce pink and green colors in a treatment similar to CVD.
   Kiriazis credits Genovese with changing the way drusy is cut so that it could be set more easily. “The sides of most drusy material used to be finished straight up and down, so there was no place to fold a bezel strip. Using Genovese’s technique, a gemstone setter could place the strip of metal along the sides of the stone and set it.”
   Natural black drusy, also known as psilomelane, is mined out and rarely, if ever, seen at market. Most black drusy that is found is quartz that has been soaked in a sugar solution for weeks. The pores in the crystal structure absorb the solution. It is then placed in a sulphuric acid bath. Treated black drusy is very popular and significant in the color spectrum because the crystals on the black surface produce a brilliantly dramatic effect. Coating drusy in precious metals like 18-karat or 24-karat gold or platinum gives drusy even more shimmer.

   While these treatments make beautiful colored stones, special care is needed when they are being made into jewelry. Drusy that has been treated with titanium or other methods cannot be polished after it is set in a piece of jewelry or the coating will come off. “Drusy is sensitive to chemicals and elements like harsh heat,” says Wilcox, adding that constant direct sunlight will fade coated or natural-colored drusy.
   Drusy’s increased popularity has affected the price and availability of the natural-colored material. “The natural-colored drusy is generally more expensive, particularly the more rare material like chrysocolla, cobalto calcite and uvarovite,” says Lasater. “The mineral and natural patterns in the stone also affect the price. Drusy can cost from $15 to $65 per carat for quartz and chalcedony and up to $300 per carat for the more rare drusy.”
   Whether it is natural or enhanced, expensive or affordable, drusy’s glittering effect makes it eye-catchingly unique and unforgettable.

Article from the Rapaport Magazine - June 2015. To subscribe click here.

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