sedimentary

Agate

Silicon dioxide (chalcedony), SiO2

Hardness of 6.5 to 7 on the Mohs scale, exhibits waxy luster, conchoidal fracture, and displays characteristic concentric color banding.

Identified October 24, 2026More sedimentary →

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Physical properties

Hardness of 6.5 to 7 on the Mohs scale, exhibits waxy luster, conchoidal fracture, and displays characteristic concentric color banding.

Formed by the deposition of silica from groundwater in the cavities of igneous or sedimentary rocks over millions of years.

Widely used in ornamental jewelry, decorative carvings, and precision instruments like mortars and pestles.

Agate was highly prized in ancient civilizations as a talisman and for making intaglio seals and ornate vessels.

Easily identified by its distinctive banded patterns and waxy texture; commonly found in volcanic rock cavities worldwide.

Fossil-bearing concretion, possibly containing a fossil shell or other organic inclusion

Calcareous concretion; exact fossil and host-rock composition are not identifiable from the image

Fossiliferous Sedimentary Rock

Sedimentary limestone with invertebrate fossil imprint

Sandstone or Siltstone

Arenite (if sandstone)

Sandstone

Arenite

Shale

Shale (clastic sedimentary rock)

Shale (or Mudstone/Siltstone)

Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)