sentences:  A quarry is first recorded in 1390.The stone comprises angular fragments and grains, up to 40mm in diameter, of sandstone, chert, minerals, granite and volcanic rocks, all embedded in a matrix of finer sands and clay.As the stone was formed from sediment laid down by flash flooding in semi-arid conditions, the stone fragments are not rounded by the wearing of water, as are sedimentary deposits laid down in the sea.