mineral
Tumbled gray chalcedony (agate-like quartz)
Chalcedony, microcrystalline SiO₂
AI-generated identification · may be incorrectMohs hardness 6.5–7; translucent gray with a waxy to vitreous luster and no visible crystal faces. It has a cryptocrystalline quartz structure and no distinct cleavage; the smooth shape is from tumbling.
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Physical properties
Mohs hardness 6.5–7; translucent gray with a waxy to vitreous luster and no visible crystal faces. It has a cryptocrystalline quartz structure and no distinct cleavage; the smooth shape is from tumbling.
Formation & geological history
Silica-rich fluids deposited microscopic quartz in cavities and fractures, commonly in volcanic rocks. Such deposits form across many geological ages; the image alone cannot establish this specimen’s age or locality.
Uses & applications
Used for beads, cabochons, small jewelry pieces, and decorative objects; this modest tumbled piece is mainly a collectible.
Geological facts
Chalcedony is quartz whose crystals are too small to distinguish without magnification; banded varieties are commonly called agate.
Field identification & locations
Look for its even, waxy translucence, hardness, and conchoidal fracture; it occurs worldwide in volcanic cavities and silica-rich deposits. The rounded, polished surface indicates a processed specimen.
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