metamorphic
Quartzite Chert Pebble
Sedimentary Chert / Metamorphic Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, brown, and brownish-orange from iron oxide staining; Luster: Dull to waxy; Texture: Fine-grained and water-worn; Cleavage: None (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Color
- Tan, brown, and brownish-orange from iron oxide staining
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, brown, and brownish-orange from iron oxide staining; Luster: Dull to waxy; Texture: Fine-grained and water-worn; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed from the accumulation of silica-rich microfossils or chemical precipitation on the seafloor, later subjected to heat and pressure. This specimen has been smoothed and rounded by river or glacial transport over thousands of years.
Uses & applications
Used as construction aggregate, decorative landscaping stone, and historically for stone tools due to its hardness and sharp fracture edges.
Geological facts
Iron oxides like limonite or hematite provide the rusty orange-brown staining seen on the surface. These stones are incredibly durable and can survive millions of years of erosion.
Field identification & locations
Identified by its high hardness (it will scratch glass) and lack of visible grains. Found globally in riverbeds, glacial tills, and beaches. Collectors look for unique banding or internal patterns.
