mineral

Quartz (Agate/Chalcedony)

Silicon Dioxide (SiO2)

Hardness of 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline structure, conchoidal fracture, specific gravity around 2.60 to 2.65, translucent to opaque yellow/brown coloration.

Identified July 28, 2026More mineral →

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Physical properties

Hardness of 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline structure, conchoidal fracture, specific gravity around 2.60 to 2.65, translucent to opaque yellow/brown coloration.

Formation & geological history

Formed through the deposition of silica-rich groundwater within cavities of volcanic or sedimentary rocks, often over millions of years.

Uses & applications

Used in jewelry, ornamental carvings, lapidary arts, and historically for tools or weapons.

Geological facts

Chalcedony is a microcrystalline variety of quartz. It has been used since ancient times for intricate seals, signet rings, and ornamental objects.

Field identification & locations

Can be identified by its conchoidal fracture, waxy luster, and lack of visible crystal faces without magnification. Commonly found in riverbeds, gravel deposits, and volcanic cavities worldwide.