sedimentary

Chert (Jasper/Agate variety)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale), Color: Red, tan, and white banding, Luster: Waxy to dull, Crystal structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture)

Hardness: 6

Identified April 10, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale), Color: Red, tan, and white banding, Luster: Waxy to dull, Crystal structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture)

Formation & geological history

Formed through the accumulation of silica-rich microfossils or chemical precipitation from silica-rich fluids in sedimentary basins. This specimen appears to be a weathered fragment of banded chert or jasper common in various geological ages.

Uses & applications

Used historically for stone tools due to its sharp edges; currently used for decorative stone, lapidary work (jewelry), and as a collector's specimen.

Geological facts

Chert is so hard it can strike sparks from steel. Varieties with red coloring from iron oxide are often called Jasper, while translucent banded varieties are called Agate.

Field identification & locations

Identify in the field by its hardness (cannot be scratched by a steel knife) and its smooth, shell-like (conchoidal) fracture surfaces. Commonly found in stream beds and coastal gravels.