What is Granite? Granite is the most popular stone type used in countertop applications today. Granites are some of the hardest of the common countertop stones, offering high levels of resistance to abrasion and scratching. Granites are made up of several different minerals, each mineral having a different hardness. Granites contain quartz, feldspars, biotite, amphibole, ferrous titanium oxides, and other mineral combinations. Limestone is a sedimentary stone with at least 50% calcite or calcium carbonate content. Almost all limestone is composed of grains or fragments of biologic origin, ranging from fossils to dinosaur bones. Most limestone is marine in origin, composed of micro-sized fossils of marine organisms like the shells found on most beaches. It is very common to find pieces of shells in limestone tiles.