The later, heavy bladed industry, provisionally dated to the period c.5000 - 4000 Cal BC, is better represented than the earlier tradition and at present represents the first substantial activity on the site. Tanged points, basally retouched flakes, rods, scrapers, and edge-worked blades are well represented. One possible feature, a hearth-pit (F47) with evidence for several phases of re-use has been dated to the mid fifth millennium Cal BC (4658-4369 Cal BC; 5650 ±80 BP (Beta-89312)). A nearby tree-pit (F223) may also date to this period to judge from the nature of its fill. Unfortunately, no flintwork was directly associated with either feature. It is, however, notable that the later Mesolithic flintwork concentrates in the south-eastern sector of the Billown Quarry Site, an area that seems to have become something of a focus for activity in the fourth millennium Cal BC.