The Pre-Cambrian Structure of Missouri 119 
variations in texture and color and accessory mineral studies 
(47) show the borders of the main mass to consist of a number 
of different types. Scattered outcrops of granite in the eastern 
part of the area covered by the Mine La Motte quadrangle and 
in the Higdon quadrangle may belong to the main body. There 
are three types of granite in Ste. Genevieve County on Jonca 
and Pickle creeks, one of which corresponds to that of the main 
mass. 
Along the southern border of the main mass there is a medium- 
grained, red granite which is distinguished from the rest of the 
granite by its heavy mineral assemblage (47). It is also char- 
acterized by the presence of a number of dikes striking northeast 
which are not found within the main mass. The name Silver 
Mine granite will be used in referring to this rock. 
The granite at Graniteville is red and coarse-grained ; much 
of it is porphyritic; pegmatitic phases occur in the southern 
Part of the area. No basic dikes are found in this body of 
granite. Near Cornwall, a very coarse granite is cut by a basic 
dike two feet wide which strikes N. 55° W. Coarse-grained 
granite also outcrops southwest of Coldwater where it is cut by 
a basic dike 20 feet wide which strikes N. 45° W. (45). Tolman 
and Koch (47) classified the granite near Van Buren and near 
Coldwater with the Graniteville granite on the basis of heavy 
mineral assemblages. They also found considerable amounts of 
the same type granite within the main granite area, Granites 
which appear to be thus related to the granites occurring at 
Graniteville will be called Graniteville granite. 
Fine-grained, red granite, here called the Ironton granite, 
°ccurs in two outcrops west of Ironton. Near Hogan there are 
two outcrops of granite which is rather fine-grained and may 
belong to the same period of intrusion as that at Ironton. Tol- 
man and Koch (47) described a fine-grained granite, which oc- 
Curs between Fredericktown and Knoblick, which may also be- 
long to the same generation of granite as that at Ironton. 
__A brownish or dark-colored granite occurs near Skrainka 
Hill, in the Mine La Motte quadrangle and has been described 
