mineral

Quartz Geode (with possible Manganese or Goethite coating)

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Clear to white crystals with dark brown/black druzy coating; Luster: Vitreous to dull; Crystal structure: Hexagonal/Trigonal (tiny drusy crystals); Cleavage: None; Specific gravity: 2.65

Hardness: 7 on Mohs scale
Color: Clear to white crystals with dark brown/black druzy coating
Luster: Vitreous to dull

Identified March 17, 2026More mineral →

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Physical properties

Formation & geological history

Formed as secondary minerals in hollow cavities of sedimentary rocks (limestone/dolomite) or igneous rocks. Mineral-rich water seeps into the void, precipitating crystals over thousands of years.

Uses & applications

Primary use is in decoration, mineral collecting, and metaphysical displays. Industrial quartz is used in glass making and electronics.

Geological facts

Geodes are essentially 'pocket' environments. The dark coloring on this surface is often a thin layer of iron or manganese oxides that coated the quartz crystals during a later stage of the geode's formation.

Field identification & locations

Identify in the field by looking for rounded, lumpy nodules that feel lighter than solid rock. Found commonly in Brazil, Mexico, and the Midwestern US (Keokuk region).

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