Tool stone
The term tool stone has multiple meanings.
In archaeology, a tool stone is a type of stone that is used to manufacture stone tools.
Alternatively, the term can be used to refer to stones used as the raw material for tools.
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.