Practical Field GeologyMcGraw-Hill Book Company, 1912 - 273 páginas |
Otras ediciones - Ver todas
Términos y frases comunes
acid alidade alteration angles assay Associates barite beds blue bodies boundaries brown button calcite cassiterite chalcopyrite charcoal chlorite cleavage cleave color colorless compass contact mineral contour coördinates copper country rock crucible crusts crystalline schists cupel deposits depth determined dikes disseminated distance drill elevation fault plane feldspar fibrous field flame fluorite folding formation fracture galenite garnet geologist gold grains granite gray green hexagonal horizontal igneous rocks intersection limestone luster magnetite masses material measurements metallic metamorphic rocks method mica mining monoclinic monoclinic crystals muffle orthoclase orthorhombic outcrop oxidation pale parallel pegmatites plane table portion prisms pyrite pyroxene quartz sample scale schists sedimentary rocks serpentine sheet silicates silver slope solution sometimes specimens sphalerite stadia STREAK strike and dip sulphides surface Tests 32 Tests 40 texture tion topographic triangulation usually vein zone vertical yellow
Pasajes populares
Página v - Omer smote 'is bloomin' lyre, He'd 'eard men sing by land an' sea; An' what he thought 'e might require, 'E went an
Página 116 - ... but the position of that from d, further in, shows that before the material could be filled out to the outer arc it would be over-running at d. "While the line EFG is the farthest limit to which the crest can be carried, it does not follow that the foot of the dump will run out to the property-line at all points. For instance, with the material falling away at an equal angle on all sides, it is evident that F cannot be pushed out far enough to cover the extreme corner without over-running on...
Página 114 - ... In the previous case the upper edge of the dump was regular and the outer one irregular. In this, the limits of a portion of the outer edge are set by the property-line, and the upper edge will, in consequence, be irregular. As before, we have the crest of the dump starting out from B and C, Fig. 9, the two points on the contour through A at the given limiting distance of 200 ft. For a short distance the crest will be circular, with its center at A, and the outer edge will be found as before....
Página 121 - A FOLDED VEIN OR SEAM. Let Fig. 12 be a contour-map of an area on which an irregular outcrop has been partly located, as, for instance, at the stations marked with an X. At various other points, as 6, 9, 11, 19, drill-holes have been sunk and the seam located at the depths noted. The form of the folded seam may be determined if we can establish its contour-lines corresponding to those on the surface, and where these seam-contours intersect those of the surface of equal elevation we have points on...
Página 123 - ... which the seam lies. Elsewhere it has weathered away. The probable depth of the seam at any point may be obtained by subtracting the elevation of the seam from that of the surface, as indicated by the respective contours for that point. For instance, at G the depth is 690 ft. less 655 ft., or 35 feet. The value of this contour-method, where the outcrop is overgrown or obscured by soil, is obvious. An excellent example of its application will be found in the Masontown Folio of the US Geological...
Página 103 - Meeting, March, 1910.) MANY questions arising in the work of the mining engineer may be solved quickly and with sufficient accuracy by the methods of descriptive geometry; but, unfortunately, this subject is more often considered from a mathematical view-point than as an effective tool for solving practical problems. Some of the principles involved are merged into the ordinary operations of mechanical drawing, and are used unconsciously by the engineer in his every-day work. The rest are stowed away...
Página 117 - To PLOT THE OUTCROP OF A VEIN, WHICH MAY BE CONSIDERED AS A PLANE SURFACE. Descriptive geometry methods may be used to determine the probable outcrop of a vein. First, let the vein be free from faults and foldings, and the strike and dip be known for some definite position, as A in Fig. 11. Draw an end-view looking up the strike-line. For convenience, let this end-view be drawn with the line XX through A perpendicular to the strike as the horizontal plane through A. Let the series of lines parallel...
Página 116 - ... without having the dump over-run the side-line. From a and a', then, swing arcs with mn as a radius. These arcs limit the position of the crest so far as a and a
Página 145 - Ore Deposits at the Contacts of Intrusive Rocks and Limestones, and their Significance as regards the General Formation of Veins...
Página 116 - These arcs limit the position of the crest so far as a and a' are concerned. Similarly, for b and b' on the 900-ft. level, arcs swung with m'n' as a radius locate the crest so far as b and b' are concerned. Continuing this process for the intersection of each contour-line and the property-line, we obtain a series of arcs. The innermost arc, or the one towards the uphill side, limits the crest. Drawing a fair line tangent to the inside arcs, we have the crest EFG. An arc not used, such as that from...