mineral
Rounded agate or chalcedony pebble
Microcrystalline quartz, SiO₂; identification is uncertain from the photo
AI-generated identification · may be incorrectLikely hardness 6.5–7 Mohs, waxy to dull luster, brown-gray with cream and rusty-orange bands. Quartz has a trigonal crystal structure; the pebble shows no obvious cleavage and a rounded, worn surface.
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Physical properties
Likely hardness 6.5–7 Mohs, waxy to dull luster, brown-gray with cream and rusty-orange bands. Quartz has a trigonal crystal structure; the pebble shows no obvious cleavage and a rounded, worn surface.
Formation & geological history
Formed as silica-rich chalcedony, commonly filling cavities or fractures in volcanic rocks, then rounded by water or sediment transport. Its age cannot be determined from appearance alone.
Uses & applications
Small chalcedony pebbles are collected and sometimes used in jewelry or lapidary work; this specimen appears unworked.
Geological facts
Agate is banded chalcedony, but a photograph cannot confirm whether the visible pattern is true agate banding or surface staining.
Field identification & locations
Look for translucent edges, curved bands, and a glassy-to-waxy surface; a hardness test or closer inspection can help distinguish it from other pebbles. Chalcedony occurs worldwide, often in volcanic terrain and stream gravels.
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