What observable features of a rock might tell you it was an igneous rock?
porous surface and a deep red or brown color . some of those rosks are transparent and black with a glassy texture. Answer: Granite has a grainy texture composed of visible mineral crystals. Basalt is usually fine grained with a black or black-green color. Pumice can appear full of small bubbles and will float on water. Volcanic cinders are usually dark red to dark black and appear porous. Obsidian will be black to dark brown and opaque to semi-transparent with conchoidal fracturing.