sedimentary
Chert (often found as Flint)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: typically tan, brown, or black in this weathered state; Luster: waxy to dull; Crystal Structure: Trigonal (microscopic); Cleavage: none, features conchoidal (shell-like) fracture; Specific Gravity: 2.65.
- Hardness
- 6
- Color
- typically tan, brown, or black in this weathered state
- Luster
- waxy to dull
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: typically tan, brown, or black in this weathered state; Luster: waxy to dull; Crystal Structure: Trigonal (microscopic); Cleavage: none, features conchoidal (shell-like) fracture; Specific Gravity: 2.65.
Formation & geological history
Formed through the precipitation of silica in sedimentary environments, often replacing organic material or filling cavities in limestone. It can occur as nodules or bedded deposits throughout Paleozoic to Cenozoic eras.
Uses & applications
Historically used for stone tools (arrowheads, scrapers) due to its sharp edges; used today as a decorative aggregate in landscaping or as a flint for fire-starting. This specific shape suggests potential use as a lithic tool or a naturally occurring ventifact.
Geological facts
Chert nodules are often associated with fossils. When chert is dark and high-quality, it is commonly referred to as flint. This specimen shows a tapered, conical shape which can occur naturally or through intentional knapping by early humans.
Field identification & locations
Identify by its hardness (it will scratch glass and steel) and its distinctive conchoidal fracture. It is ubiquitous in limestone regions and along riverbeds where harder minerals concentrate after erosion.
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