TD6.3 In the lower part of TD6.3 (TD6 subunit 3), 84 stone tools were recovered, predominantly small, unmodified quartzite pebbles with percussive damage—probably inflicted from pounding items such as bone—as opposed to manufacturing more specialised implements. Although 41% of the section's assemblage consists of flakes, they are rather crude and large—averaging —either resulting from rudimentary knapping (stoneworking) skills or difficulty working such poor quality materials. They made use of the unipolar longitudinal method, flaking off only one side of a core, probably to compensate for the lack of preplanning, opting to knap irregularly shaped and thus poorer quality pebbles. TD6.2 Most of the stone tools resided in the lower (older) half of TD6.2, with 831 stone tools. The knappers made use of a much more diverse array of materials (although most commonly chert), which indicates they were moving farther out in search of better raw materials. The Sierra de Atapuerca features an abundance and diversity of mineral outcroppings suitable for stone tool manufacturing, in addition to chert and quartz namely quartzite, sandstone, and limestone, which could all be collected within only of the Gran Dolina. They produced far fewer pebbles and spent more time knapping off flakes, but they were not particularly economic with their materials, and about half of the cores could have produced more flakes. They additionally modified irregular blanks into more workable shapes before flaking off pieces. This preplanning allowed them to use other techniques: the centripetal method (flaking off only the edges of the core) and the bipolar method (laying the core on an anvil and slamming it with a hammerstone). There are 62 flakes measuring below in height, and 28 above . There are three conspicuously higher quality flakes, thinner and longer than the others, which may have been produced by the same person. There are also retouched tools: notches, spines, denticulates, points, scrapers, and a single chopper. These small retouched tools are rare in the European Early Pleistocene. TD6.1 TD6.1 yielded 124 stone tools, but they are badly preserved as the area was also used by hyenas as a latrine, the urine corroding the area. The layer lacks pebbles and cores, and 44 of the stone tools are indeterminate. Flakes are much smaller with an average of , with ten measuring below , and only three exceeding . They seem to have been using the same methods as the people who manufactured the TD6.2