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amount appear associated average beds bodies Bulletin carry cement cent character clay coal Colorado Company considerable consists contains copper country rock County Creek crystals deposits depth described developed dikes distance district drift east elevation exposed extends fault feet field fissure formation geology gneiss gold grains granite gravel ground Hill important inches included iron known lead less lies limestone locally located lode lower masses material miles mill minerals mines Mountain nearly occur origin ounces outcrop oxidized pegmatite places porphyry portion present principal probably production prospects quartz range region reported Resources ridge River Road rock sand sandstone schists shaft shale shown side silver situated slope southwest Springs stone strike structure surface Survey thickness thin tion tunnel upper usually valley vein wide width zinc zone
Seite 380 - Preliminary report on the geology of the common roads of the United States. In Fifteenth Ann. Rept., pp. 259-306. 1895. - The geology of the road-building stones of Massachusetts, with some consideration of similar materials from other parts of the United States.
Seite 282 - The porphyritic gneiss may grade into less or more highly pegmatized gneiss, and from the latter into regular pegmatite. This gradation may be between two separate beds or from one part to another of the same bed. In those beds or portions of beds where there has been little pegmatization monazite occurs sparingly. The same is true where pegmatization has been complete, and but little of the original gneiss remains. It is, then, the beds of gneissic rock which are rich in secondary quartz, and contain...
Seite 280 - ... down in some cases. The partial concentration of monazite in the top layer of soil is caused by the washing away of the clay and other light decomposition products of the rock. The supply of monazite in the stream gravels in favorable areas is often replenished by the wash from the hillside soils during rains, especially where the hills have any considerable slope and the land is cultivated. Under such conditions the streamgravels are often worked two or more times in a year.
Seite 7 - ... afford a better idea of the work which the Survey as an organization is carrying on for the direct advancement of mining interests throughout the country than can readily be obtained from the more voluminous final reports. The first two bulletins of this series included numerous papers relating to the economic geology of Alaska. In view of the rapid increase of economic work, both in Alaska and in the States, and the organization of a division of Alaskan mineral resources distinct from the division...
Seite 444 - This field embraces the largest area of known phosphate beds in the world, and at some future time it will doubtless furnish a large part of the world's production of commercial fertilizer. The development of intensive farming as the result of the reclamation of arid lands in the West will afford an increasing home market.
Seite 280 - The saprolite or rotted rock underlying the richer deposits of monazite was at some places sluiced down to depths of from a few inches to a foot or so, along with the overlying gravels. At other places, small amounts were removed and washed separately for the monazite they contain.
Seite 423 - SHALER, NS, WOODWORTH, JB, and MARBUT, CF The glacial brick clays of Rhode Island and southeastern Massachusetts. In Seventeenth Ann. Rept., pt. 1, pp. 957-1004. 1896.
Seite 279 - The quartz grains of the granite remain as sand mixed through a clayey matrix. This quartz sand is almost everywhere to be seen at the immediate surface, from which the clays have been washed by rains. Where Carolina gneiss and granite are intimately associated, or where pegmatization has been extensive in a body of Carolina gneiss, there results a sandy soil, characteristic of granite, through which are scattered pebb,les of hematite and ferruginous cyanite, characteristic of the Carolina gneiss....