sedimentary

Chert (specifically Pink/Tan Chert)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Hardness: 7 on Mohs scale (scratches glass); Color: tan, pinkish-gray, or buff; Luster: waxy to dull; Crystal Structure: Cryptocrystalline (hexagonal system at microscopic level); Cleavage: none, breaks with characteristic conchoidal fracture.

Hardness: 7 on Mohs scale (scratches glass)
Color: tan, pinkish-gray, or buff
Luster: waxy to dull

Identified March 31, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolarians or diatoms) or by chemical precipitation from silica-rich fluids. It often occurs as nodules in limestone or chalk beds. This specimen appears to be a weathered fragment from a sedimentary basin.

Uses & applications

Historically used for making sharp tools and arrowheads; currently used in construction aggregate, road surfacing, and as a durable material for decorative landscaping.

Geological facts

Chert has been used by humans for hundreds of thousands of years because of its ability to break into razor-sharp edges. Flint is a variety of chert. It is very chemically stable and highly resistant to weathering.

Field identification & locations

Identify in the field by its hardness (cannot be scratched by a steel knife), smooth waxy feel, and the way it breaks into curved, shell-like (conchoidal) surfaces. It is found globally in sedimentary rock outcrops.

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