The best-identified collection of bluestone is a feldspathic sandstone, which here at Central Supply we call Pennsylvania bluestone. This name is resulting from a dark-blue-colored sandstone primary found in Ulster County, New York created during the Middle to Upper Devonian Period in the Paleozoic Era, approximately 370 to 345 million years ago by depositing the sand-sized grains by slowly moving water in the "Catskill Delta".
The Catskill Delta was formed from runoff water from the Arcadian Mountains (“Ancient Appalachians”) which enclosed the terrain where New York City is now built. This Delta was a narrow cluster from southwest to northeast and today contains the main geological vein for the high-quality stone to quarry in Northeast Pennsylvania. This type of sandstone may appear in many other hues besides blue at certain angles.
This variety of Pennsylvanian sandstone defined as feldspathic greywacke is desired for its gorgeous look, durability, and strength and is produced by about 150 typically small quarries in neighboring areas of Pennsylvania and New York.
Historically farmers and their families used them into stone walls, some made houses that have lasted more than two centuries, others were put into stone arch bridges, office buildings or churches.
Quarrying industry originated in colonial times but n the 19th Century, rapidly became a key industry for capitalists and mine laborers in North America.
Although stone quarrying in northeast Pennsylvania and Upstate NY come to an end as a major industry in the area in the early 20th Century, because of mass use of concrete and depletion of easily accessible stone, quarrying successfully continues in the 21st century.