mineral

Quartz Geode

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale), Color: tan to gray exterior with clear to yellowish internal crystals, Luster: Vitreous (glassy) inside and dull/earthy outside, Crystal structure: Trigonal/Hexagonal, Specific gravity: 2.65

Identified May 24, 2026More mineral →

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Physical properties

Formation & geological history

Formed in cavities of sedimentary or volcanic rocks. Mineral-rich waters seep into hollow bubbles or voids, precipitating crystals over millions of years. This specimen appears to be of the 'Cold Water' sedimentary variety common in the Midwestern US.

Uses & applications

Primarily used for decorative purposes, educational specimens, geological collecting, and sometimes in landscaping or metaphysical markets.

Geological facts

The word geode comes from the Greek word 'Geoides' meaning earth-like. Unlike a nodule (which is solid), a true geode is hollow inside, though many small ones are completely filled with crystals.

Field identification & locations

Identify in the field by looking for rounded, bumpy, or 'cauliflower-like' nodules that feel lighter than they look (if hollow). Found commonly in limestone beds or volcanic ash deposits in areas like Iowa, Indiana, and Mexico.