mineral

Quartz Geode

Crystalline Silver Oxide (SiO2) in Calcareous Host

Hardness: 7 on Mohs scale (for crystals); Color: White to colorless crystals in a tan/beige outer shell; Luster: Vitreous to greasy; Crystal structure: Trigonal/Hexagonal; Cleavage: None/Conchoidal fracture.

Hardness: 7 on Mohs scale (for crystals)
Color: White to colorless crystals in a tan/beige outer shell
Luster: Vitreous to greasy

Identified July 5, 2026More mineral →

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Physical properties

Formation & geological history

Formed within hollow cavities in sedimentary or volcanic rocks. Mineral-rich groundwater precipitates crystals over thousands of years as it seeps through the porous outer shell. Often found in limestone or shale beds of various geological ages.

Uses & applications

Primarily used for educational specimens, home decor, rock collecting, and occasionally as a source for quartz in lapidary work.

Geological facts

The word 'geode' comes from the Greek word 'Geoides' meaning 'earth-like'. While they look like ordinary rocks on the outside, they contain hollow cavities lined with crystals. Some of the largest geodes can be big enough for a person to stand inside.

Field identification & locations

Identified by a round or egg-shaped exterior that feels lighter than a solid rock of the same size. When shaken, some may rattle if crystals have broken loose. They are common in the Midwestern United States, Brazil, and Mexico. Collectors should look for 'lumpy' nodules in limestone outcrops.

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