sedimentary
Agate
Silicon Dioxide (Chalcedony), SiO2
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline crystal structure, conchoidal fracture with no true cleavage, and a specific gravity of 2.58 to 2.64. Colors vary widely due to impurities, often showing banded patterns of white, grey, red, orange, and brown.
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline crystal structure, conchoidal fracture with no true cleavage, and a specific gravity of 2.58 to 2.64. Colors vary widely due to impurities, often showing banded patterns of white, grey, red, orange, and brown.
Formation & geological history
Forms primarily within cavities of volcanic and metamorphic rocks through the deposition of silica from groundwater solutions, often layer by layer over millions of years.
Uses & applications
Used in ornamental objects, jewelry, lapidary arts, precision instruments, and as collectible mineral specimens.
Geological facts
Agate has been used since antiquity for gemstones, seals, and amulets, notably by the ancient Greeks and Romans. It is often associated with balancing emotional and physical energy.
Field identification & locations
Can be identified by its distinctive concentric banding, waxy luster, and translucency. Found globally, especially in regions with historic volcanic activity like Brazil, India, Germany, and the USA.
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