Scenery, Science and Art: Being Extracts from the Note-book of a Geologist and Mining EngineerJ. Van Voorst, 1854 - 323 páginas |
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Scenery, Science and Art: Being Extracts from the Note-book of a Geologist ... David Thomas Ansted Visualização integral - 1854 |
Scenery, Science and Art: Being Extracts from the Note-book of a Geologist ... David Thomas Ansted Visualização integral - 1854 |
Scenery, Science and Art: Being Extracts from the Note-book of a Geologist ... David Thomas Ansted Visualização integral - 1854 |
Palavras e frases frequentes
abundant Algiers Alpujarras Amposta appearance Aubin Aveyron bands beauty beds Berja Cagliari chain character Cheliff Cherchel chiefly Chiffa coal coal-field coast coloured commenced considerable consists copper crossing cultivated Délémont deposits distance district east Ebro elevation entered exist extend extremely feet France French geological gorge granite ground hills houses inhabitants interesting island Kanawha kind labour land less limestone lode lofty Madrid Mediterranean miles mineral mines Moorish mountains natural nearly numerous obtained occupied oolite passing peculiar picturesque plains Porrentruy present principal Pyrenees pyrites Pyrmont quantity quartz quartz bands range reached remarkable rich ridge rising river road rocks Rodez Roman sandstone Sardinia scenery schists seams seen shales side Sierra de Gador Sierra Nevada soon Spain Spanish stream streets surface Tarragona Tenez tertiary thickness tion Tortoli town tract traveller Valencia valley various vegetation veins village walls whole
Passagens conhecidas
Página 278 - an auriferous pyrites, occurring in a whitish or white schist. The vein is ' worked at a depth of 90 feet, or thereabouts, but has been proved to 160, and ' remains uniform. It yields about (0-00000919 its weight) 6 dwts. of gold to the ton, and some silver. Of this there seems an indefinite quantity; and from the Buckingham mine there were obtained about 1500 ounces of ' gold in the course of last year. The expense of getting and reducing is ' estimated at 15 shillings per ton, but there is much...
Página 279 - The actual breadth of this belt I had no means of exactly ascertaining, but it certainly exceeds 200 yards, and is probably much greater. It is, however, subdivided, including distinct bands of mixed quartzy threads and rotten red and yellow or greenish schists. On these repose bands of talcose or chloritic schist, which pass into an imperfect steatite, occasionally used as a firestone to line furnaces.
Página 278 - ... of all which the compositions resemble, and the planes of structure conform to, the compositions and structures of the rocks in their respective neighbourhoods. Except in this particular, and that massive quartz is more abundant, the south-western parts differ but little from the northeastern. " surface threads of copper ore were found, consisting of copper pyrites mingled " with the iron pyrites which forms the staple. These have gradually increased, " but at present there seems little chance...
Página 280 - ... and not unfrequently iron pyrites. In this schist, at a small depth, are a multitude of quartz threads, and farther down these threads come together, forming a distinct quartz band, often enclosing portions of the schist. The gold disseminated indifferently near the surface, amongst the quartz, rotten schists and enclosing walls, gradually collects together into threads, usually ranging with the schistose portions within the quartz band.
Página 280 - The enclosing rock, which within 20 feet of the surface is hardly to be " distinguished from the vein, gradually changes below this point, and within a " depth of 10 or 15 feet becomes a hard compact talcose schist, often containing " fine-garnets, and not unfrequently iron pyrites. In this schist, at a small depth, " are a multitude of quartz threads, and farther down these threads come to" gether, forming a distinct quartz band, often enclosing portions of the schist.
Página 278 - Rcconnoiuance of Virginia, p. 63. f " Between the Buckingham and Eldridge mines, and the Garnett and ' Moseley, abundance of iron and quartz appear at the surface. The latter mines ' are opened on rocks about 1) mile east of the former, and probably belong to 1 different bands of quartz.
Página 281 - The enclosing slates and schists are indeed rotten and disintegrated, the quartz broken and weathered, the iron highly oxidized, and the whole band or vein readily reduced to mud. This, too, is especially the case within a small depth from the surface. But decomposition will hardly account for a change in thick, well-defined quartz bands, to small but distinct threads, from an inch or two to a foot thick, perfectly detached from each other, and imbedded in innumerable thin flakes of coloured schists....
Página 274 - ... taken from veins now in place, the heaviest masses " being always found nearest to the auriferous strata, and the particles of gold" dust at the greatest distance from them."—Ibid, p. 351. " Washings were formerly carried on successfully in a small gully running " through the (Waller) estate; and on searching for the veins whence the " auriferous sands had been removed, they were found distinctly marked close " to the surface."—ANSTED, Scenery, Science, and Art, p. 284. " In the alluvial...
Página 279 - ... to line furnaces. All these are on the east or lower side of the series. In the middle, between the two well-marked auriferous bands which next succeed, is a certain thickness of hornblendic greenstone (d) hard, and tolerably compact.