This distribution is presently hard to explain in terms of geological and glacial history, and needs further examination. SRC is found over a very wide area, from eastern Saskatchewan through southwestern Manitoba, the eastern Dakotas, much of Minnesota and presumably into northern Iowa. This material is extremely variable, especially in color. The spongy or ropy texture of the cortex is also distinctive, when cortex is present. SRC is a difficult material to work.
Cobbles are extremely tough, and even breaking open a raw cobble can be difficult.
Presumably this was a response to the tenacity of the material, which impedes even the earliest stages of reduction. Once SRC was reduced to the form of a tool, however, it the tool should also have be tough and durable. Distribution ranges from parts of southern Manitoba through the eastern Dakotas, much of Minnesota and presumably into northern Iowa. In Manitoba, RRC would be identified as either Cathead Chert or Selkirk Chert, both of which are known from bedrock outcrops. In Minnesota, where these materials are known only from glacial drift, they are commonly grouped under the broader category of Red River Chert.