At various places in the Archaean areas of Missouri the granites and porphyries are cut by dikes of basic rocks which usually trend N. E. and: S. W. but occasionally in other directions. The dike rocks are comparatively constant in composition. When holo-crystalline they are a diabase, or an olivine diabase, and when less perfectly crystallized they generally correspond to diabase porphyrite.
Proceedings of the Iowa Academy of Sciences
©1890 Iowa Academy of Science, Inc.
"Notes on Missouri Minerals,"
Proceedings of the Iowa Academy of Science, 1(Pt. 2), 33-35.
Available at: https://scholarworks.uni.edu/pias/vol1/iss2/21