sedimentary
Agate
Silicon dioxide (Chalcedony), SiO2
Hardness of 6.5 to 7 on the Mohs scale, typically brown, red, grey, or banded colors, waxy to vitreous luster, cryptocrystalline crystal structure, conchoidal fracture with no cleavage, specific gravity of 2.6 to 2.65.
Identified More sedimentary →
Explore Agate in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness of 6.5 to 7 on the Mohs scale, typically brown, red, grey, or banded colors, waxy to vitreous luster, cryptocrystalline crystal structure, conchoidal fracture with no cleavage, specific gravity of 2.6 to 2.65.
Formation & geological history
Forms primarily within cavities of volcanic and metamorphic rocks through the deposition of silica-rich groundwater solutions over millions of years.
Uses & applications
Used in jewelry, ornamental carvings, decorative items, and historically for precision instruments and mortars/pestles.
Geological facts
Agate is one of the most popular and varied forms of chalcedony, named after the Achates River in Sicily where they were found in ancient times.
Field identification & locations
Identified by its waxy luster, conchoidal fracture, and sometimes translucent banding. Commonly found in regions with past volcanic activity worldwide.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Fossiliferous Concretion
Septarian Concretion containing Brachiopods/Crinoids
fossil
Quartz pebble
Silicon dioxide (SiO2)
sedimentary
Generic Pebble / Rock Fragment
Lithic fragment / Weathered rock
sedimentary
Banded Siltstone / Mudstone Pebble
Siltstone / Argillite
sedimentary
Sedimentary Sandstone
Arenite (Sedimentary Rock)
sedimentary