128 ' TRANSACTIONS OP THE [mAY 23, 



(vol. ii, p. 475), and the recent mining excitement in the vicinity 

 of Beep Creek, a station on the old pre-railway stage route, has also 

 prompted a brief sketch from W. P. Blake (Age of the Limestone 

 Strata of Deep Creek, Utah, etc., Amer. Geol. Jan. 1892, p. 47, re- 

 printed in the Eng. and Min. Jour., Feb. 27, p. 253). It appears 

 that one of the Basin Ranges, the Ibapah, runs along the borders 

 of Utah and Nevada, and consists in a large degree of limestones 

 Avhich Blake regards as Lower Carboniferous from the specimens of 

 Productus contained in them. These are pierced by granite and 

 other igneous rocks which have wrought extensive contact meta- 

 morphism in the limestones, and caused the formation of some 

 interesting minerals briefly noted by Blake. Evidently the igneous 

 rocks also pierce slates, as is shown by the following description of 

 slide No. fi. 



No. 1 of dike adjoining claim near Fish Spring Camp is rhyolite. 

 It shows a microcrystalline ground-mass with some glass, abundant 

 idiomorphic phenocrysts of quartz, a crystal or two of sanidine, and 

 a very little biotite, sometimes bleached. Rhyolites have already 

 been recorded by Emmons from the region. 



No. 2, from a granite outcrop that forms the mass of Clifton 

 Mountain near Gold Hill, is a hornblende granite with considerable 

 plagioclase, and with apatite, and titaniferous magnetite. 



No" 3, an altered limestone from Monaco, near Clifton, showed 

 more physical than mineralogical changes. 



No. 4, from the American Desert, betAveen Dugway and Fish 

 Spring, and about three miles east of Fish Spring, is a hypersthene- 

 andesite of great beauty. The ground-mass is glass, with a few 

 little plagioclase needles. The large plagioclase crystals are zonal 

 and often full of inclusions of the groundmass. A grain or two of 

 magnetite appear. Almost the only othcsr mineral is hypersthene, 

 in rounded prismatic crystals, of strong characteristic pleochroism, 

 and in great abundance. The extinction is invariably parallel, and 

 the optical properties such as would be expected. One stray augite 

 was also detected. 



Hypersthene was strangely overlooked by Zirkel in his report for 

 the 40th Parallel Survey, but has been announced by Iddings to be 

 quite widespread in the volcanic rocks of the Great Basin and the 

 Pacific Slope. ^ Cross has also described an interesting occurrence 

 in the Buffalo Peaks,'' Colorada, and in the paper has given a quite 

 complete review of the known localities for these rocks in other 

 parts of the world. Up to the publication of his paper they were 

 but few and often questionable. 



No. 5, from two miles east of RockwelPs Ranch, Cherry Creek, 

 is another andesite of different character. It has large brown 



1 Hague and Idrlin<;s, Notes on the Volcanoes of Northern Califoj-nia, Oregon, 

 and Wa.shington Territory. A. J. S., Sept. 1883, p. 222. Also Volcanic Rocks 

 of the Great Basin, idem, June, 1884, p. 453. 



2 C. W. Cross, Bulletin No. 1, U. S. Geol. Survey. 



