igneous
Dark igneous rock with white feldspar/quartz patches
Likely porphyritic basalt or andesite; white patches may be plagioclase feldspar or quartz
AI-generated identification · may be incorrectDark gray to black, fine-grained groundmass with conspicuous pale crystals or mineral aggregates; likely Mohs hardness 5–7 and vitreous to dull luster. Exact composition and crystal structure cannot be confirmed from the image alone.
Identified More igneous →
Explore Dark igneous rock with white feldspar/quartz patches in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray to black, fine-grained groundmass with conspicuous pale crystals or mineral aggregates; likely Mohs hardness 5–7 and vitreous to dull luster. Exact composition and crystal structure cannot be confirmed from the image alone.
Formation & geological history
Probably formed as lava cooled, with larger crystals growing before the remaining melt solidified; its geological age and precise setting cannot be determined visually.
Uses & applications
Commonly used crushed for aggregate and road base; this small specimen is mainly of educational or collecting interest.
Geological facts
The pale inclusions contrast with the finer dark matrix, suggesting a porphyritic texture, though some may be mineral-filled cavities or attached material.
Field identification & locations
Look for a fine dark matrix containing larger, lighter crystals; a fresh broken surface and hardness tests can help distinguish feldspar from quartz. Similar volcanic rocks occur in many volcanic regions worldwide.
