mineral

Quartz Geode

Silicon Dioxide (SiO2)

Hardness of 7 on the Mohs scale, clear to white or brownish color, vitreous to greasy luster, trigonal crystal system, conchoidal fracture with no true cleavage, and a specific gravity of 2.65.

Identified August 6, 2026More mineral →

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Physical properties

Hardness of 7 on the Mohs scale, clear to white or brownish color, vitreous to greasy luster, trigonal crystal system, conchoidal fracture with no true cleavage, and a specific gravity of 2.65.

Formation & geological history

Formed when mineral-rich groundwater or hydrothermal solutions seep into cavities within sedimentary or volcanic rocks, slowly precipitating silica layers over millions of years to form microcrystalline or macrocrystalline quartz linings.

Uses & applications

Used in decorative items, mineral collecting, lapidary arts, and occasionally for metaphysical purposes.

Geological facts

Geodes start as hollow bubbles in rock, often formed by gas trapped in volcanic lavas or through the dissolution of nodules in sedimentary rock like limestone.

Field identification & locations

Easily identified by its outer weathered limestone or basalt crust contrasted with a sparkling inner cavity lined with quartz crystals. Common worldwide, particularly in regions with limestone deposits or volcanic activity.