sedimentary
Chert / Fossilized Burrow Cast
Microcrystalline Quartz (SiO2) with Trace Carbonates
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
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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.
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