sedimentary
Chert (Yellow Jasper/Flint)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs), Color: Yellow to brownish-tan, Luster: Waxy to vitreous, Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.65
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs), Color: Yellow to brownish-tan, Luster: Waxy to vitreous, Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.65
Formation & geological history
Formed primarily through the accumulation of silica-rich organic remains or chemical precipitation within sedimentary rock layers like limestone or chalk. Many specimens date back to the Cretaceous or Paleozoic eras.
Uses & applications
Used historically for stone tools due to its sharp edges; modernly used for decorative landscaping, lapidary work (jewelry), and as a silica source in glass manufacturing.
Geological facts
Flint and Jasper are both varieties of chert. When struck against steel, chert can create sparks, which led to its extensive use in flintlock firearms and early fire-starting kits.
Field identification & locations
Identify in the field by its smooth, waxy texture and characteristic shell-like (conchoidal) fractures. It will easily scratch glass but cannot be scratched by a steel knife. Common in riverbeds and limestone outcrops.
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