Ironstones

Continental Shelf. Most consohdated mineral deposits found on the continental shelf are identical to those found on land and are only fortuitously submerged. Exceptions include those laid down in shallow marine seas or basins in earlier geochemical environments such as bedded ironstones, limestones, potash, and phosphorites. 

Eisenstein, m. ironstone, iron ore. — spatiger —, spathic iron ore, siderite. 

Gelbe, n. yellow (of an egg), yolk. Gelbeisen-erz, n., -stein, m. yellow day ironstone (okriges) yellow ocher copiapite. -kies, m. pyrite. gelbeln, v.i. turn yellowish. 

De Duve (and other authors) consider the source to be iron, which as Fe2+ provides one electron per Fe atom when subject to solar UV irradiation. The Fe3+ generated can be precipitated from solution with Fe2+ as a mixed oxide (FeO Fe2C>3 = FesOzt). This is found today in the form of black-band ironstone, an ore which is between 1.5 and 3.5 billion years old and was produced by interaction of Fe2+ with oxygen produced by light-converting bacteria. (The figure of 3.5 billion years is, however, not accepted by some scientists see Sect. 10.1). 

Clays Clay Min. 42 409-415 Gehring, A.U. Karthein, R. (1990) An ESR and calorimetric study of iron oolitic samples from the Northampton Ironstone. Clay Min. 25 303-311... 

Schwarz, T. Germarm, K. (1993) Ferricretes as a source of continental oolitic ironstones in northern Sudan. Chem. Geol. 107 259-265... 

Yapp, C.J. (1993) Paleoenvironment and the oxygen isotope geochemistry of ironstone of the Upper Ordovician Neda Formation, Wisconsin, USA. Geochim. Cosmochim. Acta 57 2319-2327... 

Conybeare, J. J., Description of a new substance found in ironstone, Annals... 

Hemingway, J. E. 1974. Ironstones. In Rayner, D. H. Hemingway, J. E. (eds) The Geology and Mineral Resources of Yorkshire. Yorkshire Geological Society, Leeds, 329-335. 

Spears, D. A. 1989. Aspects of iron incorporation into sediments with special reference to the Yorkshire ironstones. In Young, T. P. Taylor, W. E. G. (eds) Phanerozoic Ironstones, Geological Society Special Publication No 46. Geological Society, London, 19-30. 

SCHOEN (R.), 1964. Clay minerals of the Silurian Clinton ironstones,... 

This nepheline also contained 6 12 per cent, of carbon dioxide, and the sodalite 5 34 per cent, of chlorine. Sodium is also found in limestones, dolomites, asbestos, talc, ironstones, and various other minerals—vide sodium carbonate. 

The fire clay for making the bricks which line the furnace, and which is generally found in the same mine with the ironstone, varies very considerably in composition in different localities, having properties more or less suitable for the purpose, according to the absence of oxides, and the quantity of silica and alumina. Tav-lok, in his analysis of the rocks of the coal-measures at the Hartley pit, gives the following... 

Tho crude materials used in England in the manufacture of fine earthenware, are Cornish stone and China clay, a kind of kaolin brought from Cornwall, two varieties of plastic clay, both of which burn white, and chalk-flints. That class called ironstone china is made from ft mixture of plastic clay, kaolin, Comish stone in excess, and silica, Hie formula of which is subjoined —... 

Statement 1. Bituminous sand is an aggregate of sand, clayey matter, oil and water. The sand consists mainly of quartz particles of 50 to 200-mesh size and smaller, but also of particles of other minerals including mica, rutile, ilmenite, tourmaline, zircon, spinel, garnet, pyrite, and lignite. Clay occurs interbedded with the bituminous sand itself. Ironstone nodules of all sizes up to eight inches in diameter occur in the bituminous sand beds, especially in the southern part of the deposit. The oil is viscous, naphthenic, and of a specific... 

Sedimentary rocks with the highest arsenic concentrations largely consist of materials that readily sorb or contain arsenic, such as organic matter, iron (oxy)(hydr)oxides, clay minerals, and sulfide compounds. Arsenian pyrite and arsenic-sorbing organic matter are especially common in coals and shales. Ironstones and iron formations are mainly composed of hematite and other iron (oxy)(hydr)oxides that readily sorb or coprecipitate arsenic. Iron compounds also occur as cements in some sandstones. Although almost any type of sedimentary rock could contain arsenic-rich minerals precipitated by subsurface fluids (Section 3.6.4), many sandstones and carbonates consist almost entirely of minerals that by themselves retain very little arsenic namely, quartz in sandstones and dolomite and calcite in limestones. 

Ironstone Eastern England, United Kingdom 12 samples 37-400 Palumbo-Roe et al. (2005)... 

Palumbo-Roe, B., Cave, M.R., Klinck, B.A. et al. (2005) Bioaccessibility of arsenic in soils developed over Jurassic ironstones in eastern England. Environmental Geochemistry and Health, 27(2), 121-30. 

Iron formation A chemically precipitated Precambrian sedimentary or metamorphosed sedimentary rock consisting of thin layers rich in iron minerals (such as hematite, Fe203, and magnetite, FesOzO and usually quartz (compare with ironstone). 

Ironstone A Phanerozoic iron-rich sedimentary rock (compare with iron formation). 

Schoen (1964) calculated from X-ray data that the secondary chlorite in the Clinton ironstones had the following composition (MgAl)2.s(Fe)3.5(Si2.6s A. 3S)Oi0(OH)8, with the 2 1 layer having more Fe than the hydroxide sheet. Co-existing, primary 7 A chamosite from which much of the chlorite formed has a similar composition. 

Chamosite appears to be the finest grained and most abundant mineral in this group. It occurs in lateritic clay deposits (Brindley, 1951), both as oolites and matrix in sedimentary ironstones (Hallimond, 1925), in hydrothermal deposits (Ruotsala et al., 1964), in shales (Drcnnan, 1963), in Recent shallow-marine deposits (Porrenga, 1966) and in estuarine sediments (Rohrlich et al., 1969). It is probable that chamosite is more abundant than commonly realized however, Drennan (1963) has pointed out that it is extremely unstable in a leached and oxidized environment and is not likely to persist as an allogenic mineral. 

Youell (1958) from chamosite-kaolinite beds of Northampton sand ironstone formation at Wellingborough, England. 

Figure 10.18. Number of occurrences of Phanerozoic ironstones (upper diagram, data from Van Houten and Bhattacharyya, 1982) and odlitic limestones (lower diagram, data from Wilkinson et al., 1985) as a function of geologic age. The relative sea level curve is that of Hallam (1984). Minima in occurrences appear to correlate with times of sea level withdrawal from the continents and major cycles of orogenesis (Caledonian, Hercynian, and Alpine).

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