Gem Silica

Chalcedony has a waxy luster, and may be semitransparent or translucent. It can assume a wide range of colors. Gem silica is a bluish green to greenish blue variety of chalcedony that receives its vivid color from the presence of copper. It is often known as “chrysocolla chalcedony” or “gem silica chrysocolla.”

As a variety of chalcedony, gem silica has a Mohs hardness of 7 and is durable enough for use in almost any jewelry design. The best specimens have a pleasing blue color with strong saturation, a uniform translucence, and a lack of inclusions.

Gem silica appears in small bubbles in chrysocolla veins. Only a few locations have produced noteworthy amounts of gem silica. Most of these locations have been productive for only a few years. Deposits are usually small in size and volume (in the range of kilograms). Therefore gem silica can be mostly found in small and very exclusive jewelry shops and pieces of jewelry with gem silica are either unique pieces or limited to very small editions. High quality gem silica can sell for prices of up to 4000 $US per kilogram rough stone.

Be aware of the fact that most valuable gem materials have their impostors, and gem silica is not an exception to this rule. Chalcedony is a porous material and easily absorbs liquids. The color of gem silica can be temporarily enhanced by placing it in water. Absorbed water enriches the gem’s color.

Clear and milky chalcedony is easily dyed. Chalcedony colored by this method should not be sold as “gem silica,” as that would be a misnomer, but some merchants have done it. Buy gem silica only from a dealer who you believe is trustworthy and knowledgeable.