sedimentary

Chert Geode with Quartz Druzy

Microcrystalline Quartz (SiO2) with macrocrystalline Quartz

Hardness: 7 on Mohs scale; Color: Tan, beige exterior with pink/white interior; Luster: Vitreous to waxy; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Tan, beige exterior with pink/white interior
Luster: Vitreous to waxy

Identified May 17, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed via chemical precipitation of silica-rich fluids within cavities or nodules in sedimentary limestone or dolostone during diagenesis. Common across various geological eras from Paleozoic to Cenozoic.

Uses & applications

Primarily collected as display specimens; historically used for stone tools (flint) due to conchoidal fracturing; used in jewelry when polished or cut into cabochons.

Geological facts

The tiny crystals covering the surface are known as 'druzy' quartz. Chert is extremely durable and weather-resistant, which is why these nodules often remain on the surface after the host limestone has weathered away.

Field identification & locations

Identify by its extreme hardness (cannot be scratched by steel) and the presence of microcrystalline layers surrounding a crystalline center. Common in riverbeds and limestone outcrops.

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