sedimentary
Agate
Silicon Dioxide (Chalcedony), SiO2
Hardness: 6.5 to 7 on the Mohs scale; Color: Varied, often banded with white, gray, blue, red, green, and brown; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline quartz); Cleavage: None, exhibits conchoidal fracture; Specific Gravity: 2.58 to 2.64
- Hardness
- 6
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5 to 7 on the Mohs scale; Color: Varied, often banded with white, gray, blue, red, green, and brown; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline quartz); Cleavage: None, exhibits conchoidal fracture; Specific Gravity: 2.58 to 2.64
Formation & geological history
Formed primarily within the cavities of volcanic and metamorphic rocks through the deposition of silica from groundwater solutions over millions of years.
Uses & applications
Used extensively in jewelry, ornamental carvings, polished display specimens, and industrial knife-edge bearings and mortars.
Geological facts
Agate is one of the most popular stones used in lapidary arts and was historically used by ancient civilizations for amulets, seals, and ornaments.
Field identification & locations
Identified by its distinctive concentric banding patterns, waxy luster, and conchoidal fracture. Commonly found in riverbeds, glacial tills, and volcanic regions worldwide.
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