Bisbee daily review., 1906-01-14
ON DEPOSITS QF
 TONOPAH DISTRICT First DisCOVercdin AprillgO by James 1. Butler a
 PfOSpector

Ore deposits were discovered in the ToDopah mining district, Nevada, in April, 1900, by MT. James l.. Butler. In the fali and winter of 1902 Mr. J. E.. Spurr, of the United States Geologi cal Survey, visited the district and studied it. He repeated his visit the following summer. and in the fall of 1908 gave the main economic results of his Investigations to the public in the form of brief preliminary report, which the Survey listed as Bulletin No. 219. The final report, which is entitled, Geology of the Tonopah Min ing District. Nevada" has recently Teen published as Professional Paper No. 42. and is now available, free or charge to all who are interested ln the development of this important mining region.
 The geological problem presented in this district could have been solved only by a trained photographer, since the igneous rocks that carry the vein deposits have been largely covered by practically barren flows of more recent erupuves. The very careful and thor ough study of the district which Mfr Spurr has made can hardly fail to be of great practical value to the miner, as well as of scientific interest 10 the student Of ore deposits. The value and interest of the text are enhanced by the addition of seventy eight Illus trations. which include toposrapfnc and geologic maps tsone Of them ID coIorsl. diagrams. sIereograms, plans of veins and faults, geologic sections and cross sections. and photographic views of characteristic landscape feat ures.
 The rocks of the mining district are all of immediate volcanic origin, wltn the exception of a series ot water1aiu fiffs. which represent the accumula- ,rions of fine volcanic detritus in terti- ary lake. All the rocks are of terta' ry age. probably Miocene-Pliocene. The first eruptiyes of this volcanic epoch, as displayed at Tonopah, were adesites. Two audesites have been distinguish ed-the younger or earlier andesite ana the later andesite. which is sighty more basic than the earlier andesite. Subsequently, eruptions of rhyoiite and of dacite occurred at intervals for icng time and produced several of the formations mapped. which include tuffs and flows.
 The structure is so complicated tha' no general cross sections have been made. Some interesting information or faulting has, however, been obtain ed. chiefly from mine workings.
 The most important mineral veins occur in the early andesite, and do moi extend into the oYerlying rocks. The naturalization was probably caused by hot ascending waters immediately al ter the earlier andesite eruption The primary ores have gangue of quartz Adulari2, and some serieite and carbo mates, and contain silver sulphides-' such as asgenJite. polybasite and steph anste-siiver seIenide, gold in a yet un- determined form, chaicopyrite, pyrite and some galena and blende. The depth of oxidation is irregular. h the ere of the oxidized zone no important changes in the amount Of gold or sil yer, as compared with the primary ore have taken place. The ore near the surface is not a truly oxidized ore however. but is an intimate mixture of original suiphides (and selenides) together with secondary sulphides chiorides and oxides. Secondary sul pisides include argentite and pyrargy.