mineral

Quartz Geode

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: White to translucent; Luster: Vitreous to crystalline; Structure: Hexagonal (trigonal) crystal system; Cleavage: None/Conchoidal fracture; Specific gravity: 2.65.

Hardness: 7 (Mohs scale)
Color: White to translucent
Luster: Vitreous to crystalline

Identified March 17, 2026More mineral →

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Physical properties

Hardness: 7 (Mohs scale); Color: White to translucent; Luster: Vitreous to crystalline; Structure: Hexagonal (trigonal) crystal system; Cleavage: None/Conchoidal fracture; Specific gravity: 2.65.

Formation & geological history

Formed in cavities within volcanic or sedimentary rocks. Mineral-rich water seeps into hollow bubbles (gas pockets in lava or sedimentary nodules), depositing crystals over millions of years as the water evaporates or cools.

Uses & applications

Primary use is for decorative displays and mineral collecting. Large-scale quartz is used in glassmaking and electronics (piezoelectric properties), though geode specimens specifically are kept for aesthetic value.

Geological facts

Geodes are often called 'thunder eggs' when they are solid or have specific patterns. The largest quartz geodes can be big enough for a human to stand inside, though small palm-sized specimens like this one are more common globally.

Field identification & locations

Identify in the field by looking for round or egg-shaped nodules that feel unusually light for their size (indicating a hollow center). Common locations include Morocco, Brazil, Mexico, and the Midwestern United States (Iowa/Illinois). crystals will scratch glass easily.