In the natural stone industry, just like any other industry, there are choices, or different grades of materials. At some vendors they only sell one grade and act as if that is all there is. But there are actually several different grades of stone. From the very best at in ‘A’ grade to a less dense and more porous lower grade of ‘D’. When you shop with experienced and knowledgeable stone experts they will show you the different grades and let you make in informed buying choice on what suits you best.