sedimentary

Chert

Chert (Microcrystalline Quartz)

Hardness: 6.5-7, Color: Brown, tan, gray, Luster: Waxy to dull, Crystal structure: Microcrystalline, Cleavage: None (conchoidal fracture)

Identified June 13, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7, Color: Brown, tan, gray, Luster: Waxy to dull, Crystal structure: Microcrystalline, Cleavage: None (conchoidal fracture)

Forms as chemical sedimentary rock, often from siliceous oozes or replacement of limestone/chalk environments.

Historically used for making stone tools; sometimes used as a decorative stone or in tumbling.

Often called flint when found in chalk deposits. Shows conchoidal fracture which made it ideal for early tool-making.

Identified by its waxy luster, hardness (scratches glass), conchoidal fracture, and lack of cleavage. Common in many sedimentary deposits worldwide.

Fossiliferous Sedimentary Rock

Sedimentary limestone with invertebrate fossil imprint

Sandstone or Siltstone

Arenite (if sandstone)

Quartz pebble

Silicon dioxide (SiO2)

Generic Pebble / Rock Fragment

Lithic fragment / Weathered rock

Sedimentary Sandstone

Arenite (Sedimentary Rock)

Shale (or Mudstone/Siltstone)

Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)