mineral
Gray chalcedony (possibly agate)
Microcrystalline quartz, SiO₂
AI-generated identification · may be incorrectTranslucent gray-white with a waxy to vitreous luster and irregular, shell-like fracture; hardness 6.5–7 Mohs, trigonal quartz structure. The small rough fragment shows no obvious banding, so agate identification is uncertain.
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Physical properties
Translucent gray-white with a waxy to vitreous luster and irregular, shell-like fracture; hardness 6.5–7 Mohs, trigonal quartz structure. The small rough fragment shows no obvious banding, so agate identification is uncertain.
Formation & geological history
Silica-rich fluids deposited microcrystalline quartz in rock cavities and fractures, often in volcanic rocks; formation can occur across many geological ages.
Uses & applications
Used for carvings, beads, cabochons, and ornamental objects; this unworked piece is mainly a modest collecting specimen.
Geological facts
Chalcedony is a broad name for very fine-grained quartz; distinctly banded chalcedony is called agate.
Field identification & locations
Look for toughness, waxy luster, translucency, and hardness sufficient to scratch glass; common sources include Brazil, India, Uruguay, and the western United States. A photo cannot establish locality or confirm agate banding.
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