A stone tool is, in the most general sense, any tool made of stone. Although stone-tool-dependant 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. Chipped stone tools are made from cryptocrystalline materials such as chert, radiolarite, chalcedony or 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.
Ground stone tools are maufactured from larger-grained materials such as basalt and some forms of rhyolite, which are not suitable for flaking. Because of their coarse surfaces, many ground stone tools are ideal for grinding plant foods. Some ground stone tools are incidental, caused by use with other tools: manos, for example, are hand stones used in conjunction with metates, and develop their ground surfaces through wear. Other ground stone tools include adzes, celts, and axes, which are manufactured using a labor-intensive, time-consuming method of repeated grinding against a harder stone, often using water as a lubricant.
Another type of stone that may be considered an artifact, but is manifestly not a stone tool, is burnt or fire-cracked rock, also abbreviated as FCR. Fire-cracked rock is rock of any type that has been altered and split by deliberate heating. It is a feature of many archaeological sites, particularly in the south-central United States. FCR is occasionally confused with heat-treated tool stone, but the latter is a different type of material resulting from a different heating process.