Metamorphic

On average, fluorine is about as abundant as chlorine in the accessible surface of the earth including oceans. The continental cmst averages about 650 ppm fluorine. Igneous, metamorphic, and sedimentary rocks all show abundances in the range of 200 to 1000 ppm. As of 1993, fluorspar was still the principal source of fluorine for industry. 

Sources. Iron ore deposits were formed by many different processes, eg, weathering, sedimentation, hydrothermal, and chemical. Iron ores occur in igneous, metamorphic, and sedimentary deposits. Normally, as-mined iron ore contains 25 to 68% iron. 

The Utah deposit is located in southwestern Utah near Cedar City. The iron ore deposits are of contact metamorphic origin. The cmde ore contains 35 to 65% iron, primarily in the form of magnetite and goethite. Mining is done by the open pit method. The cmde ore is cmshed, screened at —75 mm (—200 mesh size) and shipped as lump ore containing 54% iron. The ore is rescreened at the steel mill to produce lump ore (10—64 mm) for the blast furnace and sinter feed (0—10 mm) for the sinter plant. 

Marble is a metamorphic, highly crystalline rock that may be high calcium or dolomitic limestone of varying purity. It occurs in virtually every color in diverse motded effects and is the most beautiful form of limestone. It is usually very hard and can be cut and poHshed to a very smooth surface. 

Quartz-Pebble Conglomerate Deposits. Known quartz-pebble conglomerate ores are restricted to a specific period of geologic time. These ore types occur in basal Lower Proterozoic beds unconformably situated above Archaean basement rocks composed of granitic and metamorphic strata. A number of commercial deposits are located in Canada and South Africa. Some subeconomic occurrences have been reported in Brazil and India... 

MetamorphicDeposits. Uranium deposits belonging to the metamorphic class occur in metasediments or metavolcanics generally, without direct evidence of post-metamorphic mineralization. Examples include the deposits at Eorstau, Austria (16). 

Talc of metasedimentary origin is formed by hydrothermal alteration of a dolomitic host rock by a silica-containing fluid. This type of deposit is typical of Montana and AustraUa. It is usually quite pure with talc content of 90 to 98% and often very white as well. Dolomite [17069-72-6], CaMg(C02)2, is the most common accessory mineral. The fourth type is of metamorphic origin, where a siUcaceous dolostone is first converted to tremolite [14567-73-8] or actinohte [13768-00-8] and then partially converted to talc. The Balmat, New York, and Death Valley, California, deposits are of this type. Tremolite, dolomite, and serpentine are common accessory minerals. This type of talc deposit has a variable talc content (30—80%), but is usually white and often commercially exploited because of the properties of its accessory minerals rather than the talc. 

Tungsten deposits occur in association with metamorphic rocks and granitic igneous rocks throughout the world (Table 2). Deposits in China constitute over half of the world reserves and over five times the reserves of the second largest source, Canada. 

Most igneous and metamorphic rocks are composed predominantly of alurninosiHcate minerals, including feldspar such as albite (NaAlSi Og) or anorthite (CaAl2Si20g) and crystalline forms of siHca such as quartz (Si02). Various mixed metal-plus-siHcon oxides such as oHvine [(Mg,Fe)2(SiO ] and... 

Barite [13462-86-7], natural barium sulfate, BaSO, commonly known as barytes, and sometimes as heavy spar, tiU, or cawk, occurs in many geological environments in sedimentary, igneous, and metamorphic rocks. Commercial deposits are of three types vein and cavity filling deposits residual deposits and bedded deposits. Most commercial sources are replacement deposits in limestone, dolomitic sandstone, and shales, or residual deposits caused by differential weathering that result in lumps of barite enclosed in clay. Barite is widely distributed and has minable deposits in many countries. 

Talc and pyrophylUte are found in metamorphic rocks that are rich in Mg and Al, respectively. Talc is most common in metamorphosed ultrabasic rocks and in metamorphosed siUceous dolomite. PyrophylUte is found in metapeUtes, including metabauxites and metakaoUnites, and in rocks enriched in Al by hydrothermal processes (106). 

A number of types of bituminous material exist and terminology is still somewhat confusing. The term bitumens in its widest sense includes liquid and solid hydrocarbons but its popular meaning is restricted to the solid and semisolid materials. The bitumens occur widely in nature and may be considered to be derived from petroleum either by evaporation of the lighter fraction under atmospheric conditions or by a deeper seated metamorphism. The purer native bitumens are generally known as asphaltites and include Gilsonite, extensively used for moulding, which occurs in Utah. 

The earth is composed of three general rock types igneous, sedimentary, and metamorphic [24]. 

Metamorphic rocks are formed from either igneous, sedimentary, or possibly other metamorphic rock masses. These original rock masses are subjected to heat. 

Bedrock is composed of competent, hard, rock formations that underlie soils. Bedrock is the foundation engineer s description of transition from soils to rock at depth. Such rock can be igneous, sedimentary, or metamorphic. Bedrock is very desirable for foundation placement. 

Slate. A dense fine-grained metamorphic rock containing mainly clay minerals. 

Another possibility is that one of the reactants is particularly mobile, this is apparent in certain solid—gas reactions, such as the reduction of NiO with hydrogen, which is a well-characterized nucleation and growth process [30,1166]. Attempts have been made to use the kinetic equations developed for interface reactions to elucidate the mechanisms of reactions between the crystalline components of rocks under conditions of natural metamorphism [1167,1168]. 

The inorganic component of soil is dominated by four elements O, Si, Al, and Fe (Jackson, 1964). Together with Mg, Ca, Na, and K they constitute 99% of the soil mineral matter (see Table 8-2). Minerals in soil are divided into primary and secondary minerals. Primary minerals, which occur in igneous, metamorphic, and sedimentary rocks, are inherited by soil... 

Equivalent igneous and metamorphic lithologies appear to weather about twice as rapidly in island-arc and younger volcanic... 

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