Blades and Blade Cores
In the archaeologist’s terminology, a blade is a flake that measures at least twice as long as it is wide. The process of making blades was highly technical.
A blade has parallel or approximately parallel edges, and parallel ridges, called arrises, that extend the length of the dorsal surface. Blades measuring more than about 40-50mm long are sometimes called macroblades, and smaller versions are called microblades. Blade-making technology arose independently in most parts of the world because the long cutting edges on blades are ideal for a variety of tasks. Blades often served as the blanks for other tool types, such as microliths and arrowpoints.
Blade-making was highly technical because the stone core must be worked in a very specific way to set up the geometries for repeated blade removal. To set up the core, flakes must first be removed to form a platform surface at the top of the core, and more flakes must be struck down the core face to create long, straight ridges. The blades are then struck in succession down the ridges to create the elongated and parallel-sided blades. The discarded blade core preserves the parallel, elongated blade scars.
Blades were often struck by direct percussion using a hammerstone or soft billet. In the historic period, hammerstones were used to make large blades by Aboriginal flintknappers in various parts of Australia. These macroblades were used on darts or hafted as knives, and were extensively traded. Similar macroblades were made from obsidian by historic flintknappers on Manus Island, off the coast of Papua New Guinea. Many of these obsidian blades, hafted as knives or spears, were collected by overseas museums. In some parts of the world, indirect percussion was used to make blades, by striking a bone or antler punch. The Grand Pressigny flint quarries in France were a locus of indirect percussion blade-making in the Neolithic period. These large honey-coloured flint macroblades were traded extensively, and archaeologists have discovered caches with hundreds of blades destined for this exchange. Blades were also made using a pressure flaking technique, creating blades and blade cores that look almost machine-made in their geometrical precision. The Aztecs in the historical period in Mexico made long blades from obsidian by holding the core in their feet and pressing off the blades with a special chest crutch. The edge of an obsidian blade is sharper than a modern steel surgical scalpel, and a small cottage industry arose in the 1980s to supply obsidian pressure blades for eye surgery. Obsidian scalpels are still in use today.
