mineral
Botryoidal Chalcedony / Quartz
Silicon Dioxide (SiO2)
Hardness of 7 on the Mohs scale; white to light tan/brownish color; waxy to vitreous luster; microcrystalline (cryptocrystalline) quartz structure; conchoidal fracture; specific gravity around 2.60 to 2.65.
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Physical properties
Hardness of 7 on the Mohs scale; white to light tan/brownish color; waxy to vitreous luster; microcrystalline (cryptocrystalline) quartz structure; conchoidal fracture; specific gravity around 2.60 to 2.65.
Formation & geological history
Formed through the deposition of silica-rich groundwater or hydrothermal solutions in cavities, vesicles, or fractures within host rocks, often creating characteristic grape-like (botryoidal) or mammillary surface textures.
Uses & applications
Commonly collected by mineral enthusiasts, used for lapidary work, cabochons, and ornamental carvings.
Geological facts
Botryoidal forms occur when many rounded crystal growths form close together, resembling bunches of grapes. Chalcedony has been used since antiquity for intaglios, seals, and decorative items.
Field identification & locations
Easily identified by its distinctive bumpy, rounded surface texture (botryoidal habit) combined with the high hardness of quartz (scratches glass). Found worldwide in volcanic and sedimentary environments.
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Septarian Pebble
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Schist
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Metamorphic
Potassium Feldspar (Orthoclase)
Orthoclase (KAlSi3O8)
mineral