Blade (archaeology)

In archaeology, a blade is a type of stone tool created by striking a long narrow flake from a stone core. This process of reducing the stone and producing the blades is called lithic reduction. Archaeologists use this process of flintknapping to analyze blades and observe their technological uses for historical purposes. Blades are defined as being flakes that are at least twice as long as they are wide and that have parallel or subparallel sides and at least two ridges on the dorsal (outer) side. Blade cores appear and are different from regular flaking cores, as each core's conchoidal nature is suited for different types of flaking. Blades are created using stones that have a cryptocrystalline structure and easily be fractured into a smooth piece without fracturing. Blades became the favored technology of the Upper Palaeolithic era, although they are occasionally found in earlier periods. Different techniques are also required for blade creation; a soft punch or hammerstone is necessary for creating a blade. The long sharp edges of blades made them useful for a variety of purposes. After blades are flaked, they are often incorporated as parts of larger tools, such as spears. Other times, the simple shape and sharpness serves the designed role. Blades were often employed in the impression process of material culture, assisting ancient humans in imprinting ornate designs into other parts of their material culture. Scrapers, used for hide working or woodworking, or burins, used for engraving, are two common such examples. Cores from which blades have been struck are called blade cores and the tools created from single blades are called blade tools. Small examples (under 12 mm) are called microblades and were used in the Mesolithic as elements of composite tools. Blades with one edge blunted by removal of tiny flakes are called backed blade. A blade core becomes an exhausted core when there are no more useful angles to knock off blades. Blades can be classified into many different types depending on their shape and size.