Bulletin - United States Geological Survey, Issue 663

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Page 20 - Specific gravity. The specific gravity of a mineral is its weight compared with the weight of an equal volume of water.
Page 50 - ... granite. Red granite crops out sparingly on the east side of Mississippi River, the largest exposure being in sec. 17, Haven Township, Sherburne County. Other outcrops, some of considerable size, appear in western Benton County. The red granite is medium to coarse grained, the feldspar crystals averaging about one-fourth of an inch in diameter. The chief minerals are feldspar and quartz, with minor amounts of hornblende, biotite, and magnetite. The feldspars (75 per cent) are mostly red or pink...
Page 49 - The rock occurs in a higher and larger dome, the bare rounded bluffs forming a prominent landmark in the Minnesota River valley. The •Morton" rock is a medium to coarse grained biotite granodiorite gneiss. The feldspars are red, and the dark minerals occur mostly in streaks and bands. In places the rock is porphyritic. Feldspars constitute the larger share of the rock, orthoclase and plagioclase being most abundant and microcline subordinate. Considerable quartz is present. The chief dark mineral...
Page 82 - An analysis of the rock is given on page 53. 95645— 18— Bull. 663 6 Physical tests made at the University of Minnesota show that under crushing stress the first crack came at 10,574 pounds per square inch and final collapse at 17,294 pounds. Under transverse breaking strain the modulus of rupture proved to be 2,048 pounds per square inch. Gray knots in the form of lenslike masses occur but are not common. The rock is exceptionally pure and even grained; on the freshly exposed quarry wall the...
Page 71 - Falls station from the west, in sec. 32, T. 116 N., R. 39 W., on the steep face of a 50 to 60 foot bluff overlooking the marshlands northeast of Minnesota River. The rock is a dark biotite gneiss. The gneissic texture is very marked, and the planes of schistosity or easy splitting, though in a few places 1 to 3 feet apart, are commonly so closely spaced that the rock is useless. In the back part of the quarry firm rock, suitable for ordinary foundation work, may be obtained. The foundation of the...
Page 38 - The specific gravity of a solid is its weight compared with the weight of an equal volume of distilled water at the temperature of 39.2 F.
Page 156 - Faribault, where the Chicago, Milwaukee & St. Paul, the Chicago, Rock Island & Pacific, and the Chicago Great Western railways intersect.
Page 81 - PI. XIII, B, p. 118.) No pyrite or other minerals which would cause stain or blemish are present. Observed with the microscope the rock is a biotite granite. The chief feldspar is orthoclase. Considerable microcline, a little plagioclase, and abundant quartz also appear. Small grains of hornblende, magnetite, inclusions of apatite, and fairly large crystals of sphene are accessory constituents. An analysis of the rock is given on page 53.
Page 151 - ... porous rough limestone appears, as it is overlain by a later fine-grained uniform Devonian limestone, nearly white in color. It occurs more abundantly to the south in Iowa. Near Le Roy its maximum thickness is not more than 15 feet, and it is interbedded with thin bands of shale. It is of much better quality than the underlying beds, being quite free of pores and very attractive in color. It has been quarried at a number of points in the vicinity of Le Roy, but only one quarry is now in operation....
Page 116 - Tho feldspars contain many inclusions of quartz, biotite, and hornblende, large enough to be seen with the naked eye. In thin section the largest feldspars are seen to be microcline; orthoclase and plagioclase are subordinate in amount. Hornblende and biotite are the prominent dark minerals, the latter associated with magnetite grains. Apatite crystals are common and of unusually large size. In uniformity of texture, size of grain,and color the rock is similar to the " Rockville "stone. Though it...

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