sedimentary
Agate
Silicon dioxide (Chalcedony), SiO2
Hardness of 6.5 to 7 on the Mohs scale, exhibits distinct concentric or parallel banding, waxy to vitreous luster, microcrystalline (cryptocrystalline) crystal structure, conchoidal fracture with no cleavage, specific gravity of approximately 2.58 to 2.64.
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, exhibits distinct concentric or parallel banding, waxy to vitreous luster, microcrystalline (cryptocrystalline) crystal structure, conchoidal fracture with no cleavage, specific gravity of approximately 2.58 to 2.64.
Formation & geological history
Formed primarily within cavities of volcanic and metamorphic rocks through the deposition of silica from groundwater solutions in rhythmic layers over long periods.
Uses & applications
Widely used in jewelry making, ornamental carvings, decorative objects, precision pendulum supports, and mortar and pestle sets due to its durability.
Geological facts
Agate is one of the most popular stones used in lapidary art and has been prized as an amulet and ornamental stone since ancient times, notably in ancient Greece and Egypt.
Field identification & locations
Easily identified by its characteristic banded patterns and waxy luster. Commonly found worldwide, especially in regions with historic volcanic activity such as Brazil, India, Madagascar, and the United States (such as Lake Superior agates).
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