To designers, Bluestone is a hard sandstone found in Susquehanna County, Northeastern Pennsylvania. The name comes from its typically blue color. It is used as a building stone and for flagstones. Because it is a sedimentary rock it can be split into slabs and, using a chisel and rocker bar is easily broken into rectangular slabs.
Note: various other rocks are also described as 'bluestone' because of their color (eg chalcanthite, a minor ore of copper). The Welsh stone used to build Stonehenge in England is also described as bluestone. The Bluestone National Scenic River runs through sedimentary rock in West Virginia.
Riven blue sandstone