Remember, many are porous, especially the popular swirl vareties. These swirl types are often not even true granites (more artistic license). Geologists use the term gneiss. Gneiss is usually made of the same material components as granite, only the stone cools more quickly in the earth’s crust. Their swirls still show the movement of the stones active molten history. The important part is that these stones, with smaller crystals, are more porous than granites with large crystals. Impregnators are needed to reduce staining.