sedimentary

Agate

Silicon dioxide (chalcedony, SiO2)

Hardness of 6.5 to 7 on the Mohs scale, waxy luster, conchoidal fracture, and microscopic fibrous quartz structure.

Identified October 17, 2026More sedimentary →

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Physical properties

Hardness of 6.5 to 7 on the Mohs scale, waxy luster, conchoidal fracture, and microscopic fibrous quartz structure.

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

Used primarily for ornamental objects, jewelry, and lapidary art due to its attractive banded patterns.

Agate has been used since antiquity in ancient Greece and Egypt for signet rings, beads, and healing talismans.

Identified by its waxy luster, microcrystalline structure, and characteristic concentric banding; 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)