mineral
Blue Chalcedony
Silicon Dioxide (SiO2)
Mohs hardness of 6.5 to 7, pale blue to lavender color, waxy to vitreous luster, cryptocrystalline structure, conchoidal fracture, specific gravity of 2.58 to 2.64
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Physical properties
Mohs hardness of 6.5 to 7, pale blue to lavender color, waxy to vitreous luster, cryptocrystalline structure, conchoidal fracture, specific gravity of 2.58 to 2.64
Formation & geological history
Formed in low-temperature hydrothermal environments, cavities, and veins within volcanic and sedimentary rocks where silica-rich fluids deposit microcrystalline quartz over geological time scales
Uses & applications
Used in ornamental carvings, gemstone jewelry, lapidary arts, and as a collector specimen
Geological facts
Chalcedony has been used since antiquity to create intaglios, seals, and beads; the blue variety is particularly valued for its calming pastel hue
Field identification & locations
Identified by its waxy luster, conchoidal fracture, and smooth blue coloration without distinct visible crystals; commonly found in deposits worldwide including the USA, Brazil, India, and Madagascar
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