igneous
Dark, fine-grained rock (possibly basalt)
Unidentified mafic volcanic rock; basalt is a tentative visual match
AI-generated identification · may be incorrectThe specimen appears dark gray to black and fine-grained, with a dull to slightly reflective surface. Hardness and mineral composition cannot be determined reliably from this photograph; basalt is typically about 5–6 on the Mohs scale and contains plagioclase and pyroxene, sometimes olivine.
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Physical properties
The specimen appears dark gray to black and fine-grained, with a dull to slightly reflective surface. Hardness and mineral composition cannot be determined reliably from this photograph; basalt is typically about 5–6 on the Mohs scale and contains plagioclase and pyroxene, sometimes olivine.
Formation & geological history
If basalt, it formed when lava cooled at or near the surface; its age cannot be determined from the image. Basalt is geologically plausible in the broader southern California region, but the specimen is too small and indistinct for a confident regional identification.
Uses & applications
Basalt is used as crushed aggregate, road material, and building stone; this small piece is mainly suitable for collecting or display.
Geological facts
The photo shows a specimen mounted among other labeled rocks, but no label can be read clearly enough to confirm its identity.
Field identification & locations
A close view of a fresh broken surface, visible grain size, and a hardness or streak test would help distinguish basalt from other dark rocks. The image does not support a more specific identification or a reliable locality determination.
