sedimentary

Agate

Silicon dioxide (chalcedony), SiO2

Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline structure, and banded appearance with variable colors.

Identified November 7, 2026More sedimentary →

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Physical properties

Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline structure, and banded appearance with variable colors.

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

Widely used in ornamental jewelry, decorative carvings, and precision instruments due to its durability.

Agate has been used since ancient times for gemstones, seals, and healing talismans, highly prized by the ancient Greeks and Egyptians.

Easily identified by its distinctive concentric banding 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)