It stretches more than three metres in length and tapers as it goes, giving it a shape that draws the eye even in repose. Locally, it has always been known as An Cloch Fhada, simply "the Long Stone," a name that needs no elaboration once you see it.

What makes the stone more than a curiosity of scale is the possibility that it once carried ogham script. Ogham is an early medieval writing system used primarily in Ireland between roughly the fourth and seventh centuries, in which letters are represented by a series of notches and strokes cut along the edge of a stone. The stone at Longstone is recorded as a possible ogham stone, meaning the markings, if they exist, have not been definitively confirmed. Whether the inscription was never completed, has been worn away over centuries of exposure, or was misread at some point in the record, is not clear. References to the stone appear as far back as 1916, in a note by Condon, and it was catalogued again in a 1994 survey by Power and colleagues, which suggests it has long attracted attention without quite settling into certainty.