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Pennsylvania Bluestone is a layered sandstone found only in the northeastern tier of Pennsylvania and the southern tier of New York. Pennsylvania Bluestone has many uses, from cut dimensional stone used in patios, walkways and stair treads to architectural stone used in buildings. It is also used for wallstone, decorative boulders, natural steps and other landscape features. The name "Pennsylvania Bluestone" is due to its predominantly blue color and because the majority of stone is quarried in Pennsylvania; it can, however, appear in many other hues besides blue. It was formed over 360,000,000 years ago during the Devonian Period as large inland seas deposited sand in the Catskill delta region. It is composed of feldspar, sand, mica (and more minerals to be added later when testing is complete) and is clear of most organic residues.

The commercial refinishing process for pennsylvania bluestone cut slabs is called thermalizing or spalling. This process incorporates water and heat to reveal the natural layers of the stone as it was deposited originally. The cutting orientation must be almost exactly along the horizontal layers. The cut slab surface is soaked with water and heated rapidly with a wide nozzle propane torch, breaking off chips of stone along their natural fault lines. The spalled slabs are called Pennsylvania River Rock or variations of this name depending on the market or origin of the stone.