The mason advised the application of a sealant on the natural stone product.  We did a side by side comparison of the stone with and without the sealer.  The verdict was definitely to go ahead and seal the stone.  This is a very quick and easy maintenance step that can be done for less than $20 in supplies.  Re-application is suggested, but we can wait a year or two and see how it looks.  Zero skill is required, you just apply with a rag and let dry.