CHAPTER III. 
SEDIMENTARY FORMATIONS. 
CARBONIFEROUS SYSTEM. 
HOMESTAKE LIMESTONE. 
DISTRIBUTION. 
The Homestake limestone outcrops in or around the andesite 
laccolith areas and immediately in contact with the andesite. 
West of The Three Peaks laccolith it is exposed in a band extend- 
ing from the northern boundary of the district southwestward for 
about 3 miles and then southeastward to a point northeast of Iron 
Springs, except where, by faulting, the Cretaceous formations are 
brought into contact with the andesite for a distance of about a mile. 
Northeast of the Granite Mountain laccolith a band of Homestake 
limestone is exposed for about 2 miles. Both ends of this band are 
overlapped by the Pinto sandstone, which here again comes in con- 
tact with the andesite. At the Desert Mound, southwest of Granite 
Mountain, the Homestake limestone again appears. It is cut off 
by a fault on the west and disappears under the lake and stream 
deposits on the east. 
The Iron Mountain laccolith is bordered by the Homestake lime- 
stone on its northeast, east, south, and southwest sides, with a few 
interruptions due to faulting or covering by surface deposits. South- 
west of the laccolith the limestone has considerable width, owing to 
the fact that the surface of the supporting laccolith is nearly horizontal 
here, as shown by the tongue of andesite extending westward from 
the main mass and by the few andesite outliers in the Homestake 
limestone. On the west and north sides of the Iron Mountain lac- 
colith, as in Granite Mountain, the Homestake limestone is not 
exposed, the Cretaceous sandstones lapping against the laccolith. 
A patch of Homestake limestone is present in the Comstock iron 
deposit in the Cretaceous area southwest of the Homestake mine; 
others are scattered irregularly within the area of the Iron Mountain 
laccolith. 
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