sedimentary

Chert (with Drusy Quartz Pocket)

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Creamy white to light gray; Luster: Waxy to dull (matrix), vitreous/sparkling (druse); Crystal structure: Microcrystalline with macroscopic trigonal quartz crystals in the cavity; Cleavage: None (conchoidal fracture).

Hardness: 7 on Mohs scale
Color: Creamy white to light gray
Luster: Waxy to dull (matrix), vitreous/sparkling (druse)

Identified June 1, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in sedimentary environments. The crystalline pocket (druse) formed later as silica-rich fluids filled a small void or fossil cavity in the rock.

Uses & applications

Historically used for stone tools (knapping); currently used for road surfacing, as an abrasive, and small decorative specimens for collectors.

Geological facts

Chert of this color is often referred to as 'Flint' in certain archaeological contexts. The sparkling area in the center is a drusy quartz vug, common in carbonates and cherts where mineral-rich water has seeped into empty spaces.

Field identification & locations

Identify in the field by its hardness (will scratch glass easily) and its splintery, shell-like fracture pattern. Commonly found in limestone and chalk formations worldwide.

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