Hammer stones (also called knock stones) consist of raw rock or quartzite without further processing. They were selected based on shape, weight and manageability. Also cores of flint, runners of grinding or Reibsteinen, or waste and scrap pieces of device production have been used as impact stone. Usually they are round, rounded or cylindrical and have two striking surfaces. Handle dents were sometimes made for better handling. The impact marks (impact scars) are located in one or two main impact zones, but can also be distributed over the stone. A long service life leads to the approximation of a spherical shape.
Hammer stones work by direct impact, stone on stone or via intermediate pieces made of ivory, antlers or bones to achieve cuts . They are also used to retouch, pulverize (dyes), grind (seeds) or smash hard-shelled fruits, bones or mussels. Hammer stones were used from the early Oldowan to the end of the Iron Age .
Experimental archeology comes to the conclusion that striking stones made of flint or similar hard materials are unsuitable for working flint. While tough, relatively soft rocks are well suited as impact devices. These can absorb part of the impact energy without breaking, similar to impact devices made of bones , antlers or other organic materials. Hammer stones for working flint are almost without exception made of tough rock.
Flint impact devices were used to trim and roughen grinding stone surfaces, as well as to trim rock tools such as adze blades by pecking. Knocking marks can also occur during other activities, for example when soft-patting organic materials.
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