Rocks deposition

The majority of the fluorine ia the earth s cmst is present in the form of the phosphoms fluoride fluoroapatite [1306-05 ] Ca (P0 2F- Phosphate rock deposits contain an average concentration of 3.5 wt % fluorine. During phosphate processing these fluorine values are partially recovered as by-product fluorosihcic acid. The amount of fluorosiUcic acid recovered has grown steadily, in part because of environmental requirements (see Phosphoric acid and THE phosphates). 

The most significant deposits are in southern Nevada, in the Lake Mead area, and in the McDermitt caldera complex on the Nevada—Oregon border. In the McDermitt caldera, lithium probably originated from volcanic sedimentary rocks deposited in the caldera moat. There is evidence that areas of the caldera were hydrothermically active contributing to enrichment of lithium (14). This and other similar deposits are not economically viable as of this writing. These deposits do represent a significant lithium reserve, however, whenever large expansion in demand occurs. 

The hard rock deposits are mined mainly for feldspar with mica and quartz being accessory minerals. These deposits are extensive, often covering hundreds of square meters and are recognized by the light-colored, granite-like appearance with shiny mica flakes being a prominent feature. The mica content of these deposits ranges from approximately 6—10 wt %. 

A second separation technique is leaching, which uses solubility properties to separate the components of an ore. For example, modem gold production depends on the extraction of tiny particles of gold from gold-bearing rock deposits. After the rock is crushed, it is treated with an aerated aqueous basic solution of sodium cyanide. Molecular oxygen oxidizes the metal, which forms a soluble coordination complex with the cyanide anion ... 

Hard rock deposits are richer in tin than in the placer deposits, ranging from 0.6% up to 5% Sn. Such known deposits are located in Brazil, Canada, Bolivia, Pem and the USA. Because the tin from these ores is disseminated, beneficiation processes include a combination of gravity preconcentration and flotation. 

Titanium minerals have been recovered from both hard rock and sand deposits. Until 1945, most of the ilmenite and rutile produced commercially came from sand deposits, but nowadays, the production of ilmenite from rock deposits exceeds that of sand deposits. Rutile, however, is exclusively produced from sand deposits, although a new technology exists that recovers rutile from rock deposits. 

Anorthositic deposits - nearly all of the known commercially important rock deposits of titanium minerals are associated with anorthositic or gabbroic rocks. There are three main types (a) ilmenite-magnetite (titanoferous magnetite), (b) ilmenite-haematite, and (c) ilmenite-rutile. 

The Guadalajara titanium-bearing ore comes from a hard rock deposit consisting principally rutile and ilmenite. Over 85% of the mtile and ilmenite are liberated at relatively... 

Kimberlite in the Western Canadian Sedimentary Basin (WCSB) has been referred to as Class 2 kimberlite (Skinner Marsh 2004). A distinct classification is required because these bodies differ from the classical South African carrot-shaped vertical intrusions known as pipes , in that Class 2 kimberlites contain large volumes of volcaniclastic rocks deposited in shallow (<500 m in depth) saucer-shaped craters with feeder zones that are often difficult to locate. 

The phosphate rock deposits in the Florida region are in the form of small pebbles embedded in a matrix of phosphatic sands and clays [31]. These deposits are overlain with lime... 

As has been proposed by numerous studies (e.g., Rohl et al. 2000 Dickens 2003) the massive release of gas hydrates could modify climate. The best example for this hypothesis are sedimentary rocks deposited at around 55 Ma during the Paleocene-Eocene thermal maximum, where a decrease of 2-3%c in carbonate-carbon is interpreted as a consequence of an abrupt thermal release of gas-hydrate methane and its subsequent incorporation into the carbonate pool. 

Few metals occur in the earth s crust uncombined with others. Those that do, such as gold, silver, mercury, and some copper, are known as the native metals. Together with some native nonmetals such as carbon and sulfur, the native metals make up the relatively small group of native elements, naf-urally occurring masses of single elements that were recognized and put to use by humans in quite early times. Most metals occur in nature combined with nonmetals in the form of mineral and rock deposits, and from fhose minerals they are extracted by means of a variety of metallurgical fechniques. 

Backfill surface, which is normally used to provide a gravity drain to the workings, but often also as access for personnel and materials (synonym drift, meaning (a)) Fractured waste rock deposited into a former opencast mine void (sedimentologically similar to spoil and to gottj)... 

Owing to the limited domestic supply of rutile (a mixed titania and zirconia containing ore) much effort is being directed toward commercial development of rutile made from il-menite, an abundant Ti ore. A factor for a long term pressure on the price ofZris the probability of utilization of rock deposits of ilmenite as the principle source of Ti. Rock-type deposits do not contain Zr in recoverable quantities... 

The reservoir rocks that yield crude oil range in age from Precambrian to Recent geologic time but rocks deposited during the Tertiary, Cretaceous, Permian, Pennsylvanian, Mississippian, Devonian, and Ordovician periods are particularly productive. In contrast, rocks of Jurassic, Triassic, Silurian, and Cambrian age are less productive and rocks of Precambrian age yield petroleum only under exceptional circumstances. 

Cover illustration The cover art shows an eroding ancient Martian shoreline with sedimentary rock outcrops and ice remnants of a former lake, including rock deposits similar to those now being explored by the Mars Opportunity rover. The ancient lake is shown in the cutaway cross section at bottom right as it once may have been, with an ice-covered liquid brine lake and bubbles associated with gas hydrates and/or life. 

Phosphate fertilizers. From the extensive phosphate rock deposits in Tennessee, South Carolina, Florida, Idaho, and Montana, approximately 3 million tons of ore are used annually in the manufacture of fertilizers. The chief phosphate present in this rock is the normal calcium salt [Ca3(P04)2]. Because of its insolubility, this compound is not very useful as a fertilizer. If a phosphorus compound is to provide phosphorus that can be assimilated by growing plants, the compound must be one that is appreciably soluble. 

Ritzma, H. R., compiler, "Oil Impregnated Rock Deposits of Utah, Utah... 

Barium is naturally occurring in many types of rock. Deposits of fossil fuels and peat may also contain high levels of barium, often in the form of barium sulfate. It has been classified in the EPA s Group D (not classifiable). Because of its presence in drinking water and some adverse health effects on humans, it is regulated by the U.S. government. 

United States.—The principal deposits are in South Carolina, Florida, Tennessee, Arkansas, Utah and Wyoming. The South Carolina deposits are of Miocene age and occur both as land and river rock. They contain 25 to 28 per cent, of phosphoric oxide and 35 to 42 per cent, of lime. They were the earliest to be exploited, namely, from 1868 onwards, and in 1893 they furnished about one-fifth of the world s supply. Since this date the production has declined, while that of Florida has greatly increased. In 1913 Florida and Tennessee together produced some 96 per cent, of the total output from the United States of America. The hard-rock deposits of Florida are of Tertiary age, and they run parallel to the coast for 144 miles. After concentration by mechanical means they contain usually from 77 to 79 per cent, of calcium phosphate (more rarely up to 82 per cent.) with 3 per cent, of oxides of iron and alumina, some calcium fluoride and other constituents, and 3 per cent, of moisture. The best grades of Tennessee rock were guaranteed to contain 72 per cent, of calcium phosphate, and 65 per cent, is common. The soft rock is a phosphatic clay. The river pebbles are dark grey to black and are very cheaply obtained by dredging. 

Bastnasite is mined from hard rock deposits. Production in China is a by-product of iron ore mining while U.S, production is solely for rare-earths. Ore is recovered by drilling and blasting. The ore Is crushed, ground and subjected to flotation. The bastnasite fraction is floated off and thereby seperated from other minerals to produce a concentrate. Bastnasite can be converted directly, without separating individual rare-earths, to other derivatives such as sulphate or chloride by dissolution in acid. The following step to crack the concentrate for further processing used in the U.S. is to roast in air and then to leach with HCl. This produces an insoluble cerium rich... 

Figure 19 Secular variation in Th/Sc ratio for sedimentary rocks deposited in stable continental regions (shales) and tectonically active regions (sha-les/graywackes). Sample numbers are shown in or near boxes. Solid symbols and boxes are arithmetic means and 95% confidence intervals. Open circles are sediment averages reported by Condie (1993) (after McLennan et al, in press).

Asbestos is a fibrous mineral mined from rock deposits. There are approximately 30 types of minerals in the asbestos group. Of the six that have commercial importance, only oneotile, a hydrated silicate of magnesium that contains small amounts of iron and aluminum, oxides, is used in fiber processing. 

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