You are holding a dark (and therefore mafic), vesicular volcanic rock. you can tell it is volcanic because of the "bubbly"/porous texture, and because you found it near a cinder cone. this rock is a:

The rock that is described is scoria.

Scoria is a rock that belongs in the group of the igneous rocks, formed by the cooling of magma.

Scoria is a rock that is characterized with dark color, highly vesicular, low density because of the numerous macroscopic ellipsoidal vesicles, may or may not contain crystals, specific gravity greater than 1, sinks in water.

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