sedimentary

Chert (Yellow Jasper/Flint)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

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

Identified June 2, 2026More sedimentary →

Explore Chert (Yellow Jasper/Flint) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

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.