Gemstone Silica

Gem Silica

Gem silica is the tradename for a rare gemstone with a vivid greenish-blue hue. Also known as gem chrysocolla, it is actually a member of the chalcedony family and not, strictly speaking, a variety of chrysocolla at all.

Chalcedony is a type of aggregate quartz. When most people think of quartz, they think of macrocrystalline quartz, which includes amethyst, citrine, ametrine and smoky quartz. Yet many varieties of quartz are cryptocrystalline; they have microscopically (or submicroscopically) small crystals and are usually translucent to opaque, with a waxy, greasy or dull luster. This kind of quartz has fibrous and granular subcategories. The fibrous varieties are known under the general name of chalcedony, while the granular varieties are known as jasper.

Chrysocolla is one of the lesser known gemstones, but is notable because it is one of the few gemstones that contains copper. By chemical composition, chrysocolla is hydrous copper silicate and the copper lends it a distinctive greenish blue color that is similar to turquoise. However, chrysocolla is quite a soft mineral, rating about 2 to 4 on the Mohs hardness scale. It is often found mixed with malachite, azurite, turquoise or quartz.

Chrysocolla Mineral from Mexico

Gem chrysocolla, also known as rare greenish-blue chalcedony, gets its name because it is colorless chalcedony that has been stained by the same copper salts responsible for the distinctive color of the mineral chrysocolla. When it comes to high-quality gem silica, these specimens are characterized by their translucent to transparent nature and vibrant color saturation. They exhibit excellent consistency and clarity in terms of color. What makes them truly special is the combination of the appealing chrysocolla color with the superior hardness of chalcedony quartz.

Carnelian Chalcedony

Gem silica or gem chrysocolla is very rare, especially high-quality specimens since it forms under unusual conditions when deposits of chrysocolla are visited by silica-laden solutions. Good quality chalcedony cabochons in other colors typically sell for prices in the range of $3 to $5 per carat. However, prices for top grade gem silica can reach as high as $80 per carat. Buyers considering this highly priced material should also consider chrysoprase, a vivid green type of chalcedony that is still affordably priced.