Gem Silica: The Rare Encounter Between Chrysocolla and Chalcedony

Gem silica, also known as gem chrysocolla or chrysocolla chalcedony, is a rare and very pretty stone. It’s a stone that many people say combines the deep, mystical blues and greens of the ocean with the smooth, shiny quality of glass—that’s gem silica.

It’s made up of a special blend of two minerals: chalcedony and chrysocolla. Chalcedony, a member of the quartz family, is what gives gem silica its glassy luster and hardness, making it durable and a great choice for jewelry.

image: Dave Ault/cc

Chrysocolla is what brings in those vibrant blue and green hues. Chrysocolla on it’s own is usually too soft and fragile to use in jewelry. But when these two minerals come together in the right conditions, they create gem silica, a stone that’s not only beautiful but also durable enough to wear.

Gem Silica is pretty scarce, which means it’s not something you’ll find just anywhere. It’s mostly found in and around copper mines because chrysocolla, the mineral that gives gem silica its color, is often found in places where copper is found. Some of the best-quality gem silica comes from mines in Arizona.


Gem silica is the result of a unique natural process. It forms when silica-rich solutions percolate through rocks containing copper minerals, including chrysocolla. Over time, the silica replaces the chrysocolla, combining its structure with the rich blue and green hues of the original mineral. This process results in a material that has the durability and luster of quartz but with the distinctive color of chrysocolla.

Chemical Composition and Hardness

Chemically, gem silica is primarily silicon dioxide (SiO2), with traces of copper giving it its vibrant color. It has a hardness of 6.5 to 7 on the Mohs scale, making it comparable to other quartz family gems in terms of durability.

Geographic Sources

While Arizona is renowned for producing high-quality gem silica, it can also be found in other copper-rich areas around the world. Each location can produce gem silica with distinct characteristics, making the origin an interesting aspect for collectors.

Uses and Applications

Due to its beauty and rarity, gem silica is primarily used in fine jewelry. Its hardness and resistance to weathering make it suitable for various types of jewelry, including pieces that are worn daily. Artisans and designers value it for its vibrant color and the way it can be cut and polished to highlight its natural beauty.

Collectability and Value

The rarity and aesthetic appeal of gem silica make it highly collectible. Pieces with exceptional color and clarity can fetch high prices on the market. The value of gem silica pieces can also be influenced by the skill with which they are cut and the overall quality of the finished piece.

Care and Maintenance

Like other quartz gems, gem silica is relatively easy to care for. It should be cleaned with mild soap and water, and exposure to harsh chemicals or extreme temperatures should be avoided to maintain its luster and color over time.

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