A stone tool is, in the most general sense, any tool made partially, or entirely out of stone. Although stone-tool-dependent cultures exist even today, most stone tools are associated with prehistoric societies that no longer exist.

The study of stone tools is often called lithic analysis by archaeologists. Stone tools may be made of chipped stone or ground stone. A person who makes chipped stone implements is called a flintknapper. In addition to tools, many minerals were used to make arrow heads and spear points.

Chipped stone tools are made from cryptocrystalline materials such as chert or flint, radiolarite, chalcedony, basalt, quartzite and obsidian via a process known as lithic reduction. One simple form of reduction is to strike stone flakes from a nucleus (core) of material using a hammerstone or similar hard hammer fabricator. If the goal of the reduction strategy is to produce flakes, the remnant lithic core may be discarded once it has become too small to use. In some strategies, however, a flintknapper reduces the core to a rough unifacial or bifacial preform, which is further reduced using soft hammer flaking techniques or by pressure flaking the edges. More complex forms of reduction include the production of highly standardized blades, which can then be fashioned into a variety of tools such as scrapers, knives, sickles and microliths. In general terms, chipped stone tools are nearly ubiquitous in all pre-metal-using societies because they are easily manufactured, the tool stone is usually plentiful, and they are easy to transport and sharpen.

Paleolithic tools

Prehistoric stone-working techniques of the Palaeolithic are divided into four 'Modes' ,

The Mode 1 industries (Oldowan, Clactonian) created rough flake tools by hitting a suitable stone with a hammerstone. The resulting flake would have a natural sharp edge for cutting and could afterwards be sharpened further by striking another smaller flake from the edge if necessary (known as retouch). These early toolmakers may also have worked the stone they took the flake from (known as a core) to create chopper cores although there is some debate over whether these items were tools or just discarded cores .

The Mode 2 (eg Acheulean or Biface) toolmakers also used the Mode 1 flake tool method but supplemented it by also using wood or bone implements to pressure flake fragments away from stone cores to create the first true hand-axes. The use of a soft hammer made from wood or bone also resulted in more control over the shape of the finished tool. Unlike the earlier Mode 1 industries, the core was prized over the flakes that came from it. Another advance was that the Mode 2 tools were worked symmetrically and on both sides (hence the name Biface) indicating greater care in the production of the final tool.

Mode 3 technology emerged towards the end of Acheulean dominance and involved the Levallois technique. It is commonly associated with Neanderthal Mousterian industry. The long blades (rather than flakes) of the Upper Palaeolithic Mode 4 industries appeared during the Upper Palaeolithic. The Aurignacian culture is a good example of mode 4 tool production. Mode 5 stone tools involve the production of Microliths. Examples include the Magdalenian culture.

Polished stone tools

Ground stone tools became important during the Neolithic period. These ground or polished implements are manufactured from larger-grained materials such as basalt, greenstone and some forms of rhyolite which are not suitable for flaking. The greenstone industry was important in the English Lake District, and is known as the Langdale axe industry. Ground stone implements included adzes, celts, and axes, which were manufactured using a labour-intensive, time-consuming method of repeated grinding against an abrasive stone, often using water as a lubricant. Because of their coarse surfaces, some ground stone tools were used for grinding plant foods and were polished not just by intentional shaping, but also by use. Manos are hand stones used in conjunction with metates for grinding corn or grain. Polishing increased the intrinsic mechanical strength of the axe. Polished stone axes were important for the widespread clearance of woods and forest during the Neolithic period, when crop and livestock farming developed on a large scale.

Tool stone

Generally speaking, tools that require a sharp edge are made using cryptocrystalline materials that fracture in an easily-controlled conchoidal manner. Cryptocrystalline tool stones include flint and chert, which are fine-grained sedimentary materials; rhyolite and felsite, which are igneous flowstones; and obsidian, a form of natural glass created by igneous processes. These materials fracture in a predictable fashion, and are easily resharpened. For more information on this subject, see lithic reduction.

Large-grained materials, such as basalt, granite, and sandstone, may also be used as tool stones, but for a very different purpose: they are ideal for ground stone artifacts. Whereas cryptocrystalline materials are most useful for killing and processing animals, large-grained materials are usually used for processing plant matter. Their rough faces often make excellent surfaces for grinding plant seeds. With much effort, some large-grained stones may be ground down into awls, adzes, and axes.