mineral

Quartz Geode

Silicon Dioxide (SiO2)

Hardness: 7 on the Mohs scale. Color: White to translucent clear with a gray or green host rock. Luster: Vitreous (glassy) to waxy. Crystal Structure: Hexagonal (trigonal). Cleavage: None (conchoidal fracture). Specific Gravity: 2.65.

Hardness: 7 on the Mohs scale
Color: White to translucent clear with a gray or green host rock
Luster: Vitreous (glassy) to waxy

Identified July 21, 2026More mineral →

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Physical properties

Formation & geological history

Geodes form in cavities within volcanic or sedimentary rocks. Over millions of years, mineral-rich groundwater seeps into these hollow spaces, precipitating layers of silica that crystallize as quartz.

Uses & applications

Primarily used as decorative display pieces, for geological education, in spiritual/metaphysical practices, and as collector specimens.

Geological facts

The word 'geode' comes from the Greek 'geoides,' meaning 'earth-like.' While they look like ordinary round stones from the outside, the interior cavity is lined with crystals. Some geodes are hollow, while others are completely filled (known as nodules).

Field identification & locations

Identify by the contrast between a rough, dull exterior 'rind' and a crystalline, sparkling interior. These are commonly found in desert regions or limestone-rich areas in states like Iowa, Indiana, and Chihuahua, Mexico. Collectors look for unbroken nodules that feel lighter than they look, suggesting a hollow crystal cavity.