124 Transactions of the Academy of Science of St. Louis 
rhyolite, for the ores that have been worked on Shut-in Moun- 
tain are in the rhyolite intrusion. The granite at Graniteville 
contains no iron although it is on the fault which the iron solu- 
tions evidently followed. This indicates that the Graniteville 
granite was later than the iron and consequently later than the 
granite east of Ironton. 
At the Cornwall granite area, Tarr (43) finds the following 
relationships. Granite porphyry is intruded into the felsites and 
dark green to black felsite is intruded into both the granite por- 
phyry and the felsite country rock. Coarse-grained granite was 
intruded later as is indicated by the fact that both the black 
felsite and the granite porphyry have epidote developed in 
them by solutions from the granite. In addition, the granite 
porphyry contains inclusions of felsite but no inclusions of the 
granite. Haworth (23) mentions a dike trending northwest in 
the Cornwall granite, and, according to Tarr and Bryan(45), 
the coarse-grained granite southwest of Coldwater is intruded 
by a large, basic dike trending northwest. Other areas where 
the Graniteville granite is exposed have no basic dikes. The 
Graniteville granite has well developed joints striking northeast 
although it contains no dikes striking in this direction. The fel- 
site and Silver Mine granite include many dikes striking north- 
east although joints striking northwest occur in both the felsite 
and granite. A possible explanation of the strike of the dikes 
is that the first basic magma came close enough to the sur- 
face so that dikes could form along the joint planes while the 
later basic intrusion was deep-seated and came to the surface 
only along fault planes. The first intrusion of basic dikes was 
in the northeast rather than in the northwest set of joints as 
the former set was opened by tension. The scarcity of north- 
west striking dikes is in accordance with the conception that they 
follow faults. 
The gray granite intrudes the red granite on Jonca Creek 
and near Syenite. At both these localities the red granite re- 
sembles the Graniteville variety in heavy mineral assemblage 
(47). Mineralization at Silver Mine is probably the last re- 
corded event in the pre-Cambrian. Tolman (46) considers this 
