mineral

Quartz geode

Microcrystalline and crystalline quartz, SiO₂, likely with chalcedony and iron-oxide staining

AI-generated identification · may be incorrect

Typically Mohs hardness 7, vitreous to drusy luster, white to gray crystals, and no cleavage; the brown outer rind is likely weathered volcanic or sedimentary host rock. The hollow cavity is lined with small quartz crystals, possibly mixed with calcite or other secondary minerals.

Identified August 28, 2026More mineral →

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Physical properties

Formation & geological history

Formed when mineral-rich groundwater filled a cavity in volcanic rock or sediment, depositing chalcedony and later quartz crystals over long periods, commonly during the Cenozoic or older. The precise age and host rock cannot be determined from the photograph.

Uses & applications

Used as a decorative specimen, lapidary material, and collector display piece; attractive crystal-lined geodes may be sold as home décor or jewelry components.

Geological facts

The specimen’s hollow interior and sparkling drusy coating are characteristic of a geode, while the cream-brown rind reflects alteration and iron staining.

Field identification & locations

Identify by the rounded hollow shell and inward-pointing quartz crystals; quartz is commonly found in volcanic terrains and sedimentary cavities worldwide, including Brazil, Uruguay, Mexico, and the United States. A hardness test, acid test, and close inspection are needed to distinguish quartz from calcite.