In archaeology, ground stone is a category of stone tool formed by the grinding of a coarse-grained tool stone, either purposely or incidentally. Ground stone tools are usually made of basalt, rhyolite, granite, or other cryptocrystalline and igneous stones whose coarse structure makes them ideal for grinding other materials, including plants and other stones.
Organic and inorganic materials are processed on ground stones into edible products. They are sometimes the only artefacts preserved on archaeological sites and are found worldwide.
The adoption of ground stone technology is associated closely with the Neolithic, also called the New Stone Age. The Stone Age comes from the three-age system developed by Christian Jürgensen Thomsen. In the Levant ground stones appear in Mesolithic 2 (Natufian). In prehistoric Japan, ground stone tools appear during the Japanese Paleolithic, possibly predating adoption elsewhere in the Neolithic by 25,000 years.
Ground stones were created and used for a wide variety of reasons. Each use resulted in a different development and process by which a person created their ground stone. For example, the process for creating the head of a hammer is different from the process used to create a detailed decoration piece for one’s home. That being said, some processes are basic to most ground stone making.
When choosing what type of stone to use for a ground stone tool, toughness is the most important factor. If the stone is not tough enough to withstand hard hits and instead just flakes and cracks easily, the work done to create the tool has gone to waste. A stone that will not shear, flake, or crack when tested against large impacts is the most important aspect when choosing what kind of stone to use. Examples of this kind of stone include limestone, sandstone, granite, basalt, rhyolite and other igneous and cryptocrystalline rocks.
Cryptocrystalline rocks are good to use for ground stones because they have a very fine grain structure. This is helpful because the smaller the grains are in a rock, the harder the rock is.
