sedimentary

Chert / Fossilized Burrow Cast

Microcrystalline Quartz (SiO2) with Trace Carbonates

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs scale; Color: Tan, beige, light brown; Luster: Dull to waxy; Structure: Cryptocrystalline/Amorphous; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 6
Color: Tan, beige, light brown
Luster: Dull to waxy

Identified July 6, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs scale; Color: Tan, beige, light brown; Luster: Dull to waxy; Structure: Cryptocrystalline/Amorphous; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed through the replacement of limestone or carbonate sediment by silica-rich fluids. Likely originated in a marine or freshwater environment where trace fossils (burrows) were later silicified.

Uses & applications

Mainly of scientific interest to paleontologists and geologists. Historically used for stone tools; occasionally used as decorative garden stone or for lapidary tumbling.

Geological facts

This specimen appears to be a trace fossil, specifically a burrow cast which shows the path an organism took through soft sediment that later hardened and was replaced by silica.

Field identification & locations

Identify by its hardness (it will scratch glass) and its irregular, tube-like shape suggesting biological activity in ancient sediment. Commonly found in nodular forms within limestone beds.