Preliminary report of the United States Geological Survey of Wyoming, and portions of contiguous territories : (being a second annual report of progress), under the authority of the Secretary of the Interior . of the two principal sets of fissures or clefts. The unity of the originof all these fissures, whether they assume the form of mineral lodes,,dikes, or lines of fracture of mountain ranges, is a thought around whichI wish to cluster all the facts that can be secured. Hereafter all theseobservations will be carefully sifted, and rig. 19. those which seem to contain the elementsof truth wi
Preliminary report of the United States Geological Survey of Wyoming, and portions of contiguous territories : (being a second annual report of progress), under the authority of the Secretary of the Interior . of the two principal sets of fissures or clefts. The unity of the originof all these fissures, whether they assume the form of mineral lodes,,dikes, or lines of fracture of mountain ranges, is a thought around whichI wish to cluster all the facts that can be secured. Hereafter all theseobservations will be carefully sifted, and rig. 19. those which seem to contain the elementsof truth will be found valuable. In this connection, two illustrations ofthese fissures may be introduced, whichwill be of interest. They are made by theJewett line relief process, and are veryexcellent. One of them presents a finesection of the well-known Gregory lodeat Central City. This fissure has a strikeabout northeast and southwest. Thecountry rock is true gneiss, while the gangue of th^. lode is mostly feldspar and Gregory Lode, central City, quartz. So far as the history of its min- Colorado,eral contents is concerned, it is so well kno\^n that I need not describe-it, and the cut will explain a. 178 GEOLOGICAL SURVEY OF THE TERRITORIES. The dike is in the same mountain, not more than three hundred yardsfrom the Gregory lode. It is exposed by an artificial cut for a road up the side of the mountain, and but forthis circumstance would not havebeen visible from the surface. It isvertical, twenty feet high, and threeto four feet wide. The materials in-closed in the dike are evidently veryold basalt, yellow bulf color, withcavities filled with decomposed feld-spar. The country rock does not ap-pear to have suffered changes, but thelines of bedding are entirely inter-rupted, and curved upward. The following notes on the Sweet-water Mines were taken by Mr. Ar-thur L. Ford, the mineralogist of theexpedition: Cariso Mines. — Worked by , of South Pass City. ^ Shaftone
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Keywords: ., bookcentury1800, bookdecade1870, bookpublishe, booksubjectgeology
