Granite is a natural stone, and is therefore subject to natural variations, offering a truly unique appearance. 

Quartz countertops are man-made engineered stone countertops formed by combining 90% ground quartz (a natural hard mineral) with 8-10% resins, polymers, and pigments. This forms a very hard granite-like surface

Marble is  made from raw, natural marble that has been quarried, sliced, water blasted, buffed, and polished into the shining slabs.