Tool stone
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The term tool stone has multiple meanings. In archaeology, a tool stone is a type of stone that is used to manufacture stone tools.[1] Alternatively, the term can be used to refer to stones used as the raw material for tools.[2]
Generally speaking, tools that require a sharp edge are made using cryptocrystalline materials that fracture in an easily controlled conchoidal manner.[1] 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.
In the contemporary diamond industry a tool stone is a diamond attached to a pole, used to work a second diamond.[3]
In metal-working fragments of diamond are bonded to the edge of cutting tools.[4]
