What Is Drusy Quartz?

Quartz crystals are often used as semi-precious gems.
••• GreenSeason/iStock/Getty Images

Drusy (or druzy) is a geological term applied to quartz that forms a layer of closely spaced, small crystals that line a surface or cavity of another kind of rock. Drusy quartz, silicon dioxide, is most commonly clear or whitish, and can resemble glittering sugar or snow crystals. It occurs within geodes and lines the walls of cavities called vugs that occur within hollows and veins of rocks.

Formation

Geodes, commonly called thundereggs, are hollow, spherical rocks. They are formed by an original sedimentary concretion that was gradually replaced by redeposited hard rock, with a dense form of quartz called chalcedony forming the exterior rind. The drusy quartz forms when water containing silicon dioxide seeps through cracks and fissures in the rind, redepositing crystalline quartz in the hollow interior. Druses in vugs are usually found in mines constructed for harvesting other types of minerals or gems. They are sometimes combined with other minerals, such as yellow barite found in the Rock Candy Mountain Mine in British Columbia.

Uses

Split-open geodes containing drusy quartz are often collected and displayed. The hard, exposed, cut rind is commonly polished rather than left rough. The purple form of quartz, called amethyst, also makes druses. Vugs lined with drusy quartz are frequently chiseled from the parent rock for collecting. Fine druses are also used for jewelry, usually in earrings, brooches or pendants where crystals are at less risk of detachment upon wear.

Related Articles

Interesting Facts About Quartzite
Facts About Geodes
What Colors Are Geodes Naturally?
How to Clean Geodes
How to Tell the Difference Between a Geode & a Nodule
Most Common Types of Igneous Rocks
How to Identify Rough Gem Stones
The Differences Between Fluorite & Calcite
What is Silicon Dioxide?
How to Shape Rough Quartz Crystals Into Shards
How to Identify Basalt
What is a Sardonyx?
How to Collect Rose Quartz in South Dakota
Name Five Different Types of Limestone
Differences Between Extrusive and Intrusive Rocks
List of Igneous Rocks That Do Not Contain Quartz
How Do Rubies Form?
A List of Extrusive Igneous Rocks
How to Recognize Rough Agate
Stones Found in Arizona