Andesite

Andesite is a stone-like material.

Polished Andesite is the polished version of andesite. As with granite and diorite, it can be crafted from regular andesite.

Naturally generated
Regular andesite generates anywhere underground in rich seams, in an identical way to the other two stone types, as well as gravel and underground dirt. It is most commonly exposed to the surface in Extreme Hills biomes but can also be found regularly in other biomes.

Trivia

 * In real life, andesite is extrusive igneous rock of intermediate composition. Its intrusive counterpart is diorite.