Bulletin - United States Geological Survey, Ausgabe 484


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Seite 130 - A microscopic granular structure sometimes characterizing adjacent feldspar particles in granite in consequence of their having been crushed together during or subsequent to their crystallization. CUT-OFF. Quarrymen's term for the direction along which the granite must be channeled, because it will not split. Same as "hardway.
Seite 130 - BOULDER QUARRY. One in which the joints are either so close or so irregular that no very large blocks of stone can be quarried. CHANNEL. A narrow artificial incision across a mass of rock, which, in the case of a granite sheet, is made either by a series of continuous drill holes or by blasting a series of holes arranged in zigzag order.
Seite 22 - ... been squeezed, broken, and rotated into parallelism with the planes of schistosity. In many instances the original crystal is represented by lenses and eyes of granular feldspar and quartz, and in extreme cases all traces of the crystal are lost in the general gneissoid structure of the ground-mass. Besides the granular bands produced by metamorphism of the quartz and feldspar of the original rock, much new biotite and garnet have been formed, and, in less amounts, the other minerals mentioned...
Seite 37 - IJiddeford (fig. 39, p. 182), the granite is broken up into various polygons, which at the surface, where weathering has made inroads, resemble bowlders. Quarries opened in such places are called bowlder quarries. Another sort of irregularity in joints consists in their discontinuity or intermittence, their strike and dip for the short spaces in which they occur being uniform. HEADINGS. In some places joints occur within intervals so short as to break up the rock into useless blocks. For a space...
Seite 44 - The joint and sheet structure affords ingress to surface water, containing its usual percentage of carbonic acid, and the "rift" or "shake" structure facilitates the kaolinization of the feldspar on either side of the sheet parting by this water. As the feldspars pass into clay the rock crumbles into sand consisting of quartz, mica, and kaolin, and of feldspar in various stages of kaolinization. In some places within the range and depth of frost a large part of this work may have been done by frost...
Seite 45 - The changes in granite after it has entered into buildings or other constructions are less marked than those in the natural rock, because the blocks are not then traversed by anything analogous to sheet and joint structure, and also because the years of historic time are few compared to those of geologic time. Much has been written on the decay of granite in monuments and...
Seite 44 - Vinalhaven, 20 feet below the surface in the face of the quarry, there is a bed of granite sand 18 inches thick between two sheets, which at that point dip about 10° into the hill. On the southeast side of the Longfellow quarry, near Hallowell, some of the sheets within a wide heading include granite sand beds that are about 10 inches thick.
Seite 132 - A rock made up of flattish particles arranged in rough parallelism, some or all of which have crystallized under pressure. SCHISTOSITY. The quality of being like a schist. SEAM. Quarrymen's term for joint. SECONDARY MINERALS. Minerals whose presence is due to the alteration of the original minerals. SEDIMENTARY. A term designating those rocks that consist of particles deposited under water. SEGREGATION. The scientific term for "knot;" a collection of material separated from other material.
Seite 131 - GROUT. A term applied to the waste material of all sizes obtained in quarrying stone. GROW-ON. Quarrymen's term to designate the place where the sheet structure dies out, or the place where two sheets appear to grow onto one another. HARD-WAY. The direction at right angles to both rift and grain in which granite does not split readily. (See Cut-off.) HEADING. A collection of close joints.
Seite 23 - ... about eight miles and a width of one mile. At Hawleyville occurs another area of irregular outline, and a still larger area is found in Litchfield and Morris, northwest of Bantam Lake. Outcrops of amphibolite may be included in the Brookfield, as the two are difficult to distinguish in the field. The diorite is usually massive, but shows also gneissoid and even schistose phases. Both light and dark types are present in this formation, the former containing much quartz, and in extreme cases containing...

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