sedimentary
Chert (Jasper/Agate mix)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs scale); Color: Red, white, and grayish-blue; Luster: Waxy to vitreous; Structure: Microcrystalline/cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.65
- Hardness
- 6
- Color
- Red, white, and grayish-blue
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Red, white, and grayish-blue; Luster: Waxy to vitreous; Structure: Microcrystalline/cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.65
Formation & geological history
Formed via the accumulation of silica-rich fluids or microscopic organic remains (like radiolarians) that undergo lithification. This specimen likely formed as a nodule in limestone or through hydrothermal deposition in volcanic cavities.
Uses & applications
Commonly used for lapidary work (jewelry, cabochons), flint-knapping for stone tools (arrowheads), and as a collector's specimen. In industry, crushed chert is used for road surfacing.
Geological facts
Chert has been used by humans for millions of years to create tools because it breaks with sharp, predictable edges. This specific red and white variety is often called 'Jasper' if opaque or 'Agate' if translucent.
Field identification & locations
Identify in the field by its smooth, shell-like (conchoidal) fracture and its ability to scratch glass. It is commonly found in sedimentary rock beds or as river-worn cobbles.
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