mineral

Quartz Geode

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Clear to white crystals within a tan brownish exterior; Luster: Vitreous (glassy) inside, earthy outside; Crystal Structure: Hexagonal/Trigonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Clear to white crystals within a tan brownish exterior
Luster: Vitreous (glassy) inside, earthy outside

Identified June 2, 2026More mineral →

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Physical properties

Formation & geological history

Formed in hollow cavities of volcanic or sedimentary rocks. Over millions of years, mineral-rich groundwater seeps into the cavity, precipitating silica crystals onto the walls. Often found in formations dating back to the Mississippian or Jurassic periods.

Uses & applications

Primarily used for decorative display, crystal healing practices, educational specimens, and as a collectible for rockhounds.

Geological facts

Geodes are essentially 'rock bubbles'. While they look like ordinary round stones from the outside, they contain hollow centers lined with crystals. Brazil and Uruguay are world-renowned for giant amethyst and quartz geodes.

Field identification & locations

Identify in the field by looking for rounded, vuggy, lightweight nodules that may rattle when shaken. Common locations include Morocco, Mexico, and the Midwestern United States (Keokuk region).