combustibility woomeras lithos core flaking metamaterial kud chine edge endocarp adzes grindstones material lithic Moravac slabs biface flint pseudomorph Baljevac salta chippings Mercenaria Vinapu nanorods flintstone mudbricks Jatoba wood Moosebutter chert flintknappers slab doorcase softer Dolerite metate abrasive chisels