The flakes occasionally found at sites are probably detached from quartzite cobbles used as hammerstones. Rhyolite is less common than SRC or RRC, both naturally and at archaeological sites. The distribution of this material is not well documented. I would expect that this material occurs sporadically in glacial drift throughout the Western Resource Region. It sometimes resembles siltstone.
Rhyolite varies in texture from very fine grained and almost cherty, to more coarse and granular.
Its working characteristics vary from marginal to moderate. As better information became available, it became apparent that this identification was incorrect. This material is not similar to a brown rhyolite which occurs in northeastern Minnesota. TRS has a relatively narrow range of variation and is easily identified. Its natural color is restricted to a fairly narrow range of ocher or yellowish brown.