igneous
Rounded dark-gray rock, likely diorite or andesite
Probable diorite (plagioclase and hornblende/pyroxene); identification is limited by the image
AI-generated identification · may be incorrectCoarse-speckled, dark gray-green with lighter mineral grains and a dull surface; likely Mohs 6–7, with interlocking crystals and no obvious cleavage. Exact hardness, density, and mineral proportions cannot be determined visually.
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Physical properties
Coarse-speckled, dark gray-green with lighter mineral grains and a dull surface; likely Mohs 6–7, with interlocking crystals and no obvious cleavage. Exact hardness, density, and mineral proportions cannot be determined visually.
Formation & geological history
If diorite, formed when magma cooled slowly underground; if andesite, cooled more rapidly at or near the surface. Such rocks occur in many geological periods, and the pebble’s age and source cannot be established from the image.
Uses & applications
Commonly used as crushed aggregate, paving, and building stone; this rounded specimen is mainly suitable for collecting or decoration.
Geological facts
Its smooth oval shape suggests prolonged abrasion in a stream or on a shore; the original bedrock type is uncertain.
Field identification & locations
Look for interlocking light feldspar and dark minerals; a fresh broken surface and simple hardness tests can help distinguish diorite from finer-grained andesite or other dark rocks. Similar pebbles are common in river and coastal gravels.
