bluestone   A dense, hard, finegrained, commonly feldspathic sandstone or siltstone of medium to dark or bluish-gray color that splits readily along original bedding planes to form thin slabs. Bluestone is not a technical geologic term. It is considered a variety of flagstone, with its thin relatively smooth-surfaced slabs suitable for use as flagging. The term has particularly been applied to sandstones of the Devonian age, quarried in eastern New York, Pennsylvania and in western New Jersey, but similar stones from elsewhere may carry the same name. conneticut irregular conneticut tumbled