sedimentary
Chert (specifically Jasper/Carnelian Agate)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs scale); Color: Caramel brown to orange-red; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.65.
- Hardness
- 6
- Color
- Caramel brown to orange-red
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Caramel brown to orange-red; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.65.
Formation & geological history
Formed through the accumulation of silica-rich fluids in sedimentary environments or by the replacement of calcium carbonate. While specific age varies by location, these deposits are found in strata ranging from Precambrian to recent times.
Uses & applications
Used historically for stone tools due to its sharp edges; currently used for lapidary work, jewelry, landscape decoration, and as a collectible specimen.
Geological facts
This specimen exhibits the classic waxy luster and translucency typical of silica-based minerals. Chert variations like this were favored by early humans for making arrowheads and scrapers.
Field identification & locations
Identify in the field by its waxy texture, inability to be scratched by a steel knife, and smooth, shell-like (conchoidal) breaks. Often found in riverbeds or gravel pits.
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