sedimentary
Red Chert (Jasper)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale. Color: Opaque reddish-brown due to iron oxide impurities. Luster: Dull to waxy. Crystal Structure: Trigonal (microcrystalline/cryptocrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6-2.7.
- Hardness
- 6
- Color
- Opaque reddish-brown due to iron oxide impurities
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Opaque reddish-brown due to iron oxide impurities. Luster: Dull to waxy. Crystal Structure: Trigonal (microcrystalline/cryptocrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6-2.7.
Formation & geological history
Formed through the accumulation of silica-rich microfossils (like radiolarians) or chemical precipitation from silica-rich fluids in deep marine environments. The reddish hue indicates the presence of hematite. These deposits can range from Precambrian to Cenozoic in age.
Uses & applications
Historically used for stone tools (arrowheads, scrapers) due to its sharp edges. Modernly used for jewelry (cabochons), lapidary art, and as a landscaping stone.
Geological facts
Jasper has been used by humans for over 4,000 years; it was a favorite gemstone in the ancient world, mentioned in both Greek and Biblical texts. Because it breaks with a conchoidal fracture (smooth, curved surfaces), it was vital for early human survival for crafting sharp-edged weapons.
Field identification & locations
Identify by its opaque nature (unlike translucent carnelian), conchoidal fracture, and extreme hardness (it will scratch glass). Commonly found in riverbeds, or as nodules in limestone. Collectors should look for unique banding or 'picture' patterns.
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