sedimentary
Chert (Jasper) Pebble
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs), Color: Yellow-brown or tan due to iron oxides, Luster: Dull to waxy, Crystal Structure: Trigonal/Microcrystalline, Cleavage: None (Conchoidal fracture)
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs), Color: Yellow-brown or tan due to iron oxides, Luster: Dull to waxy, Crystal Structure: Trigonal/Microcrystalline, Cleavage: None (Conchoidal fracture)
Formation & geological history
Formed from the accumulation of silica-rich microfossils or precipitation from hydrothermal fluids within sedimentary rock layers, later tumbled and rounded by water action.
Uses & applications
Primarily used as decorative landscaping rock or aquarium gravel; industrially, silica has various manufacturing applications. High-quality jasper is used in lapidary work.
Geological facts
Chert and Jasper are among the oldest materials used by humans for toolmaking due to their hard nature and ability to produce sharp edges when fractured.
Field identification & locations
Identified in the field by its hardness (it can scratch glass), conchoidal fracture, and smooth, water-worn surface. Often found in riverbeds, glacial deposits, and gravel pits.
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