Granites are formed by silicate-rich acid magma that comes from the depths (a phenomenon favored by the tectonic movements). Close to the surface of the earth, this magma solidifies by cooling slowly into the cracks of the mantle, having sometimes diameters of hundreds of kilometers. The granites with a bigger granulation are called pegmatite.
Marble is a metamorphic rock, composed for the most part of calcite (the crystalline form of calcium carbonate, CaCo3) and is obtained through chalk’s metamorphosis. Marble owes its various colors to the impurities it contains: red to iron salts, brown to manganese salts, gray to graphite, etc.