sedimentary
Agate Geode
Silicon Dioxide (Chalcedony/Quartz), SiO2
AI-generated identification · may be incorrectHardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline crystal structure, concentric banding in black, white, and reddish-brown, conchoidal fracture with no true cleavage, specific gravity of 2.60 to 2.65.
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline crystal structure, concentric banding in black, white, and reddish-brown, conchoidal fracture with no true cleavage, specific gravity of 2.60 to 2.65.
Formation & geological history
Formed through the deposition of silica-rich groundwater solutions in cavities of volcanic or sedimentary rocks over millions of years, often in ancient hollows left by gas bubbles in lava.
Uses & applications
Used widely in ornamental carvings, jewelry, lapidary arts, and as highly prized specimens for rock and mineral collections.
Geological facts
The intricate banding patterns in agates represent successive layers of microscopic quartz crystals deposited over long periods. Geodes often contain hollow centers lined with sparkling quartz or amethyst crystal points.
Field identification & locations
Easily identified by its distinctive concentric color bands surrounding a hollow cavity lined with crystals. Commonly found in regions with volcanic activity, such as Brazil, Mexico, Uruguay, and various parts of the United States.
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