sedimentary
Chert (Jasper/Agate mix)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs scale), Color: tan, brown, and red inclusions (iron oxides), Luster: waxy to vitreous, 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: tan, brown, and red inclusions (iron oxides), Luster: waxy to vitreous, Crystal Structure: trigonal (microcrystalline), Cleavage: none (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed via the accumulation of silica-rich fluids in cavities or the replacement of limestone/chalk by silica. This process typically occurs in sedimentary environments over millions of years, often dating from the Paleozoic to Cenozoic eras.
Uses & applications
Historically used for stone tools (flintknapping); currently used for decorative purposes, lapidary work, landscaping, and as a collector's specimen.
Geological facts
Chert has been used by humans for hundreds of thousands of years to create sharp-edged tools. The red streaks in this specimen are likely Jasper inclusions, which get their color from iron impurities.
Field identification & locations
Identified in the field by its hardness (scratches glass), waxy luster on fresh breaks, and conchoidal (shell-like) fracture pattern. Commonly found in stream beds or within sedimentary rock formations.
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