Granite is an igneous rock. This means that at one time during its development, it was melted like volcanic lava. Unlike lava, however, this melted rock never reached the surface. It remained trapped inside, where it slowly cooled and crystallized, resulting in a very uniform, speckled stone that ranges in color from blacks and grays to pinks, browns, and reds. Polished granite is a very durable stone, much harder than marble.
Granite has been popularly used for commercial purposes for many years. Granite can often be found on building exteriors, interior walls, and “high-traffic” floors. Granite will withstand almost any element including heat and cold.
Wikipedia on Granite
"Granite (pronounced /ˈɡrænɨt/) is a common and widely occurring type of intrusive, felsic, igneous rock. Granites usually have a medium to coarse grained texture. Occasionally some individual crystals (phenocrysts) are larger than the groundmass in which case the texture is known as porphyritic. A granitic rock with a porphyritic texture is sometimes known as a porphyry. Granites can be pink to gray in color, depending on their chemistry and mineralogy. By definition, granite has a color index (i.e. the percentage of the rock made up of dark minerals) of less than 25%. Outcrops of granite tend to form tors, and rounded massifs. Granites sometimes occur in circular depressions surrounded by a range of hills, formed by the metamorphic aureole or hornfels." [More...]