The term tool stone has multiple meanings.
In archaeology

Archaeology

Archaeology, or archeology , is the study of human society, primarily through the recovery and analysis of the material culture and environmental data that they have left behind, which includes artifacts, architecture, biofacts and cultural landscapes...

, a tool stone is a type of stone that is used to manufacture stone tool

Stone tool

A stone tool is, in the most general sense, any tool made either partially or entirely out of stone. Although stone tool-dependent societies and cultures still exist today, most stone tools are associated with prehistoric, particularly Stone Age cultures that have become extinct...

s.
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

Conchoidal fracture

Conchoidal fracture describes the way that brittle materials break when they do not follow any natural planes of separation. Materials that break in this way include flint and other fine-grained minerals, as well as most amorphous solids, such as obsidian and other types of glass.Conchoidal...

 manner.
Cryptocrystalline tool stones include flint

Flint

Flint is a hard, sedimentary cryptocrystalline form of the mineral quartz, categorized as a variety of chert. It occurs chiefly as nodules and masses in sedimentary rocks, such as chalks and limestones. Inside the nodule, flint is usually dark grey, black, green, white, or brown in colour, and...

 and chert

Chert

Chert is a fine-grained silica-rich microcrystalline, cryptocrystalline or microfibrous sedimentary rock that may contain small fossils. It varies greatly in color , but most often manifests as gray, brown, grayish brown and light green to rusty red; its color is an expression of trace elements...

, which are fine-grained sedimentary materials; rhyolite

Rhyolite

This page is about a volcanic rock. For the ghost town see Rhyolite, Nevada, and for the satellite system, see Rhyolite/Aquacade.Rhyolite is an igneous, volcanic rock, of felsic composition . It may have any texture from glassy to aphanitic to porphyritic...

 and felsite

Felsite

Felsite is a very fine grained volcanic rock that may or may not contain larger crystals. Felsite is a field term for a light colored rock that typically requires petrographic examination or chemical analysis for more precise definition...

, which are igneous flowstone

Flowstone

Flowstones are composed of sheetlike deposits of calcite formed where water flows down the walls or along the floors of a cave. They are typically found in "solution", or limestone caves, where they are the most common speleothem. However, they may form in any type of cave where water enters that...

s; and obsidian

Obsidian

Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock.It is produced when felsic lava extruded from a volcano cools rapidly with minimum crystal growth...

, 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

Lithic reduction

Lithic reduction involves the use of a hard hammer precursor, such as a hammerstone, a soft hammer fabricator , or a wood or antler punch to detach lithic flakes from a lump of tool stone called a lithic core . As flakes are detached in sequence, the original mass of stone is reduced; hence the...

.

Large-grained materials, such as basalt

Basalt

Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...

, granite

Granite

Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...

, and sandstone

Sandstone

Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...

, may also be used as tool stones, but for a very different purpose: they are ideal for ground stone

Ground stone

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 macrocrystalline igneous stones whose coarse structure makes them ideal for...

 artifacts

Artifact (archaeology)

An artifact or artefact is "something made or given shape by man, such as a tool or a work of art, esp an object of archaeological interest"...

. 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

Stitching awl

A stitching awl is a simple tool with which holes can be punctured in a variety of materials, or existing holes can be enlarged. It is also used for sewing heavy materials, such as leather or canvas. It is a thin, tapered metal shaft, coming to a sharp point, either straight or slightly bent....

, adzes, and axes

Axes

Axes may refer to:* Axes, woodworking hand tools* The plural of axis* Axes , a 2005 rock album by the British band Electrelane* X and Y axes, or X, Y, and Z axes, perpendicular lines used in the Cartesian coordinate system...

.

In the contemporary diamond

Diamond

In mineralogy, diamond is an allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centered cubic crystal structure called a diamond lattice. Diamond is less stable than graphite, but the conversion rate from diamond to graphite is negligible at ambient conditions...

industry a tool stone is a diamond attached to a pole, used to work a second diamond.

In metal-working fragments of diamond are bonded to the edge of cutting tools.