sedimentary

Agate

Silicon dioxide (chalcedony), SiO2

Hardness of 6.5 to 7 on the Mohs scale, varying colors with banded patterns, waxy to vitreous luster, and trigonal crystal system.

Identified October 17, 2026More sedimentary →

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Physical properties

Hardness of 6.5 to 7 on the Mohs scale, varying colors with banded patterns, waxy to vitreous luster, and trigonal crystal system.

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

Used extensively in jewelry, ornamental carvings, lapidary art, and precision instruments like mortars and pestles.

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

Identified by its characteristic concentric bands, waxy luster, and conchoidal fracture; 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)