sedimentary
Jasper with Chert
Silicon Dioxide (SiO2) - Microcrystalline Quartz
Hardness: 6.5-7 (Mohs scale), Color: Variegated yellow, cream, and red (likely from iron oxides), Luster: Dull to waxy, Crystal Structure: Hexagonal (Microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.9
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: Variegated yellow, cream, and red (likely from iron oxides), Luster: Dull to waxy, Crystal Structure: Hexagonal (Microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.9
Formation & geological history
Formed from the deposition of silica in sedimentary environments, often replacing organic materials or filling cavities in volcanic rocks. The colors are due to mineral impurities like hematite (red) and goethite (yellow).
Uses & applications
Used primarily in lapidary arts for polishing, jewelry (cabochons), or as garden decorative stones. Historically used for making tools and arrowheads due to its conchoidal fracture.
Geological facts
Jasper is a variety of chalcedony. The red spots in this specimen are characteristic of jasper, while the tan, opaque areas are often referred to as common chert or jasperite depending on the region of origin.
Field identification & locations
Identify in the field by its inability to be scratched by a steel knife, its smooth waxy feel, and the way it breaks in curved, shell-like patterns. Commonly found in riverbeds and glacial till throughout North America.
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