sedimentary

Agate

Silicon Dioxide (Chalcedony), SiO2

Hardness of 6.5 to 7 on the Mohs scale, waxy luster, microcrystalline structure, and displays distinct concentric banding in various colors.

Identified October 24, 2026More sedimentary →

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Physical properties

Hardness of 6.5 to 7 on the Mohs scale, waxy luster, microcrystalline structure, and displays distinct concentric banding in various colors.

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

Widely used in jewelry, decorative ornaments, gemstone carving, and precision instruments due to its durability.

Agate was highly prized in ancient civilizations like Egypt and Greece for amulets, seals, and healing talismans.

Identified by its characteristic curved banding and waxy luster; commonly found worldwide in volcanic rock cavities.

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)