mineral
Chalcedony
SiO2 (Silicon Dioxide)
Hardness of 6.5 to 7 on the Mohs scale, typically white, grey, or light blue in color, waxy or vitreous luster, cryptocrystalline structure, conchoidal fracture with no true cleavage, specific gravity of 2.58 to 2.64.
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, typically white, grey, or light blue in color, waxy or vitreous luster, cryptocrystalline structure, conchoidal fracture with no true cleavage, specific gravity of 2.58 to 2.64.
Formation & geological history
Formed at low temperatures from silica-rich solutions circulating in the cavities and cracks of volcanic and sedimentary rocks.
Uses & applications
Commonly used in lapidary arts, making tumbled stones, beads, ornamental carvings, and low-cost jewelry.
Geological facts
Chalcedony has been used since ancient times (such as in Minoan Crete) for carved seals and intaglios because it takes a fine polish and does not stick to hot wax.
Field identification & locations
Identified by its waxy luster, conchoidal fracture, and semi-translucent appearance. Found worldwide in volcanic and sedimentary deposits.
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