Bulletin - United States Geological Survey, Ausgabe 426


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Seite 162 - ... chlorite, epidote, apatite, zircon, and magnetite. The Wadesboro-Rockingham porphyritic granite area. — This is a large area of porphyritic granite lying partly in Anson and partly in Richmond county, near the South Carolina line and to the west of Charlotte. About one mile east of the westernmost exposure of the granite the Triassic sandstones first appear, overlying unconformably the crystalline schists. Between the granites and the sandstones is an area of variable crystalline schists, principally...
Seite 131 - The mantle of red soil with ore partides ranging in thickness from a fraction of an inch to several inches, is only a few feet thick.
Seite 155 - consists of granite of varying texture and color, and of schists and granitoid gneisses derived from the granite. Included in the formation are small or local beds of schistose basalt, diorite, hornblende schist and pegmatite . . . "Keith, Arthur, US Geol.
Seite 49 - Each v.*as immersed for half an hour in the boiling solution of sulphate of soda, and then hung up to dry, this performance being repeated daily throughout the four weeks which the experiment lasted. Although as above noted this process is practically abandoned, the series of tests given was productive of certain results which are well worth a moment's consideration.
Seite 25 - ... or W., to N. 80° E. or W. Out of the total number of joint-planes measured fifty-six lie in the northeast quadrant and forty-five in the northwest quadrant; while nineteen strike in a north-south direction, as against sixteen having an east-west strike. Slickensides. — As a rule, the joint-planes show smooth, more or less polished and striated surfaces, indicating considerable movement in the rocks since the formation of the joints. Striae are developed in a thin coating of yellow to yellowish-green...
Seite 250 - ... above, the feldspathic constituent consists of the potash and soda-lime feldspars, with the potash varieties predominating. The porphyritic feldspars are chiefly orthoclase with some microcline, carrying inclusions of all the groundmass minerals. The included biotite shreds are visible macroscopically. Some of the largest plagioclase inclusions in the orthoclase phenocrysts carry, in turn, microscopic inclusions of quartz and other groundmass minerals. Twinning according to the Carlsbad and albite...
Seite 70 - The region is made up of a complex of schists, gneisses, and granites, with, in places, minor interfoliations of slates, quartzites, and limestones. This complex is further intersected by intrusions of basic eruptive rocks belonging, so far as they have been studied, to the diabasic, dioritic, and gabbroic types. To the east of...
Seite 151 - A sheet of several acres in extent may be raised in this manner, affording a bed plane approximately horizontal, to which the quarrymen can work, thus securing stone of any required thickness.
Seite 140 - University and the new municipal court building, in Washington, DC This grade of pink granite is in much demand in Chicago and other northern and central cities for use as monumental stock.
Seite 178 - ... but they represent a later stage of igneous activity. The fissures they fill were the result of various tensional strains or contractions, possibly consequent upon the cooling of the granite. In color these dikes vary from bluish gray to light and dark reddish. The texture of some aplites is so fine that the mineral particles can not be distinguished with the unaided eye ; that of others is so coarse that the feldspar and mica may be thus detected. Under the microscope the dimensions of the particles...

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