. Report of the geological exploration of the fortieth parallel . ase, this mineral reaches a considerable importance in the rock, itmay be properly called a chloritic quartzite. A few straggling garnets areobserved in the low members of the quartzite, near the horizon of the dolo-mitic limestones. In the rocks hei-e described the reader will have observed a certaingeneral family likeness to those in the main mass of the Wahsatch, in theFarmington region. The association of various mica gneisses and horn-blendic, even dioritic schists, succeeded conformably by quartzites, marksan approximate i
. Report of the geological exploration of the fortieth parallel . ase, this mineral reaches a considerable importance in the rock, itmay be properly called a chloritic quartzite. A few straggling garnets areobserved in the low members of the quartzite, near the horizon of the dolo-mitic limestones. In the rocks hei-e described the reader will have observed a certaingeneral family likeness to those in the main mass of the Wahsatch, in theFarmington region. The association of various mica gneisses and horn-blendic, even dioritic schists, succeeded conformably by quartzites, marksan approximate identity of conditions with the Wahsatch and with MedicineBc)w Range. The essential minerals of the range are quartz, orthoclase andplagioclase, biotite, muscovite, chlorite, calcite, dolomite, and hornblende,while the accessory minerals are garnet, zircon, actinolite, phlogopite, titaniciron, and apatite. CoRTEZ Range.—Among the many isolated mountain blocks whichcoiTUgate the surface of Nevada, few have greater geological interest than TIS GeoIErpl 40?aralld. < AKOHJilAN EXPOSURES. 71 Cortez Range. At Granite Cailon, directly northwest of Cortez Peak, one oftlie higher summits of the ridge, a little north of the parallel 40° 15, appearson the western flanks of the range a solitary mass of granite, surroundedby Tertiary volcanic rocks, which on the north are immense outpourings ofbuff rhyolite, and on the south high hills of quartz-propylite, culminatingin Cortez Peak. Southwest it comes in contact, for a limited distance, withthe upturned quartzites which have been referred to the Weber group of theCarboniferous, and on the extreme west its spurs are overlaid by an out-burst of diorite, which comes up in a synclinal of Carboniferous rocks. Thelonger axis of the gi-anite exposui-e is with the trend of the range, northeast,and is about five miles long, with an extent of tloi-ee miles in the oppositedirection, making a rude parallelogram, with a sharp point invading therhyo
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