sedimentary
Jasper Chert Nodules
Silicon Dioxide (SiO2) with Hematite impurities
Hardness: 6.5-7 (Mohs scale); Color: Red, brown, and tan; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline quartz; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.9
- Hardness
- 6
- Color
- Red, brown, and tan
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Red, brown, and tan; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline quartz; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.9
Formation & geological history
Formed through the precipitation of silica in sedimentary rock layers or as nodules in limestone/chalk. The red coloration is typically due to the presence of iron oxide (hematite).
Uses & applications
Used primarily in lapidary work for cabochons and jewelry, as well as for stone tools (flintknapping) historically, and as decorative gravel.
Geological facts
Jasper and chert have been used for millennia to create sharp tools and arrowheads because of their conchoidal fracture pattern, which creates razor-sharp edges.
Field identification & locations
Identify in the field by its smooth, waxy interior and sharp, glass-like fracture edges when broken. It is often found in riverbeds or within sedimentary cliff faces.
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