Likely basalt fragment

Dark gray to black, dull to weakly vitreous, fine-grained and irregularly weathered; hardness about 5–6 Mohs, typically dense, with no visible cleavage or crystals at this scale.

Formed when iron- and magnesium-rich lava cooled rapidly at or near Earth’s surface, commonly during volcanic eruptions; individual age cannot be determined from the image.

Used as crushed aggregate, road base, riprap, building stone, and occasionally as a decorative or lapidary material; this small weathered piece has negligible commercial value.

Basalt is the most abundant volcanic rock on Earth and forms much of the oceanic crust, including large lava plateaus and seafloor pillow lavas.

The specimen’s dark color, fine texture, and dense appearance support basalt, but scale and lighting prevent certainty; test for a nonmetallic streak and compare density, while a magnet may respond weakly if iron-rich. Common localities include Hawaii, Iceland, oceanic islands, and continental volcanic regions.