The stone selected for tools depended above-all on the intended task the tool was meant to perform. For instance, sharp tools require different raw material than durable or abrasive tools. If we expand our conception of tools to include vessels (tools as containers), jewellery (tools for self-identity), sculptures (tools for symbolic representations), and magic stones (tools for engaging with the spiritual world), then the catalogue of usable stones is vast indeed.
Most of the artefacts in the Museum of Stone Tools were made by flaking to produce sharp-edged cutting or scraping tools. This requires stone that is ‘isotropic’—that is, the stone breaks the same way in every direction. With isotropic stone, there is no internal structure to force the crack to travel in predetermined directions. A widespread misconception is that the flintknapper works with the structure or ‘grain’ of the stone to achieve the desired effect, but ideal stone for flaking has no grain. The journalist and avocational archaeologist Hubert Mewhinney quipped ‘for practical purposes, flint has no more grain that a drink of water.’