sedimentary

Agate

Silicon dioxide (chalcedony), SiO2

Hardness of 6.5-7 on the Mohs scale, waxy luster, microcrystalline crystal structure, conchoidal fracture, and distinct concentric color banding.

Identified October 24, 2026More sedimentary →

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Physical properties

Hardness of 6.5-7 on the Mohs scale, waxy luster, microcrystalline crystal structure, conchoidal fracture, and distinct concentric color banding.

Formed by the deposition of silica from groundwater in cavities of ancient volcanic and metamorphic rocks.

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

Agate was highly prized in ancient civilizations like Egypt and Greece as a gemstone and talisman for protection.

Easily identified by its translucent banded patterns; found globally in volcanic regions such as Brazil, Germany, and the USA.

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)