mineral

Quartz Geode in Sedimentary Matrix

Silicon Dioxide (SiO2) within a limestone/dolostone host

Hardness: 7 (Quartz crystals), 3-4 (Matrix); Color: Clear to milky white crystals in tan/brown matrix; Luster: Vitreous (glassy) crystals; Crystal Structure: Hexagonal/Trigonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 (Quartz crystals), 3-4 (Matrix)
Color: Clear to milky white crystals in tan/brown matrix
Luster: Vitreous (glassy) crystals

Identified May 4, 2026More mineral →

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Physical properties

Formation & geological history

Formed as mineral-rich groundwater seeped into hollow cavities (often fossil molds or gas bubbles) in sedimentary rock. Over millions of years, the cooling and evaporation of this fluid allowed silica to precipitate and grow as inward-facing crystals.

Uses & applications

Primary use is in mineral collecting, educational specimens, home decor, and occasionally as a source for high-quality silica in specific industrial applications.

Geological facts

Geodes are essentially 'pocket energy' of the earth. While the exterior often looks like a common uninteresting rock, the interior can hold crystals that have been protected for hundreds of millions of years. This specific specimen appears to be a 'cold-water geode' common in sedimentary basins.

Field identification & locations

Identify in the field by looking for rounded, lumpy stones that feel lighter than they look (if hollow) or show signs of white crystallization in cracks. Common in limestone outcrops or riverbeds. Use a rock hammer to carefully crack open suspected nodules.

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