sedimentary
Chert (Jasper variation)
Silicon dioxide (SiO2) - Microcrystalline Quartz
Hardness: 6.5-7 (Mohs scale), Color: Brown, tan, and yellow with concentric banding (Liesegang rings), Luster: Waxy to dull, Crystal structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.65
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: Brown, tan, and yellow with concentric banding (Liesegang rings), Luster: Waxy to dull, Crystal structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.65
Formation & geological history
Formed through the precipitation of silica from groundwater or the accumulation of silica-rich organic debris in sedimentary basins. The banding is caused by the rhythmic precipitation of iron oxides within the stone over geologically long periods.
Uses & applications
Historically used for tool making (arrowheads/knives) due to conchoidal fracture. Modern uses include decorative gravel, lapidary work (cabochons), and as a collector's specimen.
Geological facts
This specimen features Liesegang rings, which are colored bands of cement or precipitates that often look like wood grain or topographical maps. They are common in fine-grained silica-rich rocks like chert and sandstone.
Field identification & locations
Identify in the field by its hardness (will scratch glass), smooth waxy texture, and unique curved patterns. Commonly found in river beds and sedimentary outcrops globally.
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