sedimentary

Chert Nodule

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 (Mohs scale), Color: Cream, tan, or light grey, Luster: Waxy to dull, Structure: Cryptocrystalline, Fracture: Conchoidal

Identified July 1, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale), Color: Cream, tan, or light grey, Luster: Waxy to dull, Structure: Cryptocrystalline, Fracture: Conchoidal

Formed via chemical precipitation of silica-rich fluids within limestone or chalk beds. Often Cretaceous or Paleozoic in age.

Historically used for stone tools; currently used in construction aggregate and as a collector specimen.

Chert is so hard it can scratch glass and steel. It was a primary material for making arrowheads and spear points in pre-colonial times.

Identify by its smooth, waxy feel and sharp, shell-like edges when broken. Commonly found in river beds or weathering out of limestone cliffs.

Fossiliferous Sedimentary Rock

Sedimentary limestone with invertebrate fossil imprint

Sandstone or Siltstone

Arenite (if sandstone)

Quartz pebble

Silicon dioxide (SiO2)

Generic Pebble / Rock Fragment

Lithic fragment / Weathered rock

Sedimentary Sandstone

Arenite (Sedimentary Rock)

Shale (or Mudstone/Siltstone)

Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)