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After carbon, phosphorus is the most commonly detected element in archaeological iron. The typical phosphoric iron range is 0.1wt% to 1wt%P. The predominant source of phosphorus in iron is the ore smelted. Around 60% of economic UK rock iron ore formations contain over 0.2%P. Under fully reducing conditions, both in liquid-state (cast iron) and solid-state bloomery smelting (direct reduction) processes, such rock ores would be predicted to produce phosphoric iron, and bog iron ores even more so. Ore-metal-slag phosphorus ratios for bloomery iron are derived here, by means of: laboratory experiments; full-scale experimental bloomery smelting; and analysis of remains from three Medieval and two Late Roman-Iron Age iron production sites in England and the Netherlands. Archaeological ore, slag, metal residues (gromps), and iron artefacts were analysed by metallography, SEM-EDS, EPMA, and XRD. The effects of forging and carburising on phosphoric iron were studied by experiment and artefact analysis. The ore to slag %P ratio for solid-state reduction was determined to range from 1:1.2 to 1: 1.8. The ore to metal %P ratio varied from 1:0.2 to 1:0.7-1.4, depending on furnace operating conditions. Archaeological phosphoric iron and steel microstructures resulting from non-equilibrium reduction, heat treatment, and mechanical processing are presented to define the technology of early phosphoric iron. Microstructures were identified by a combination of metallography and chemical analysis. The phosphoric iron artefacts examined appear to be fully functional objects, some cold-worked and carburised. Modern concepts of 'quality' and workability are shown to be inapplicable to the archaeological material.

After carbon, phosphorus is the most commonly detected element in archaeological iron. The typical phosphoric iron range is 0.1wt% to 1wt%P. The predominant source of phosphorus in iron is the ore smelted. Around 60% of economic UK rock iron ore formations contain over 0.2%P. Under fully reducing conditions, both in liquid-state (cast iron) and solid-state bloomery smelting (direct reduction) processes, such rock ores would be predicted to produce phosphoric iron, and bog iron ores even more so. Ore-metal-slag phosphorus ratios for bloomery iron are derived here, by means of: laboratory experiments; full-scale experimental bloomery smelting; and analysis of remains from three Medieval and two Late Roman-Iron Age iron production sites in England and the Netherlands. Archaeological ore, slag, metal residues (gromps), and iron artefacts were analysed by metallography, SEM-EDS, EPMA, and XRD. The effects of forging and carburising on phosphoric iron were studied by experiment and artefact analysis. The ore to slag %P ratio for solid-state reduction was determined to range from 1:1.2 to 1: 1.8. The ore to metal %P ratio varied from 1:0.2 to 1:0.7 ¿ 1.4, depending on furnace operating conditions. Archaeological phosphoric iron and steel microstructures resulting from non-equilibrium reduction, heat treatment, and mechanical processing are presented to define the technology of early phosphoric iron. Microstructures were identified by a combination of metallography and chemical analysis. The phosphoric iron artefacts examined appear to be fully functional objects, some cold-worked and carburised. Modern concepts of 'quality' and workability are shown to be inapplicable to the archaeological material.

The Owl Head mining District is located in south-central Pinal County, Arizona, within the Basin and Range province. Land forms, particularity pediments, characteristic of this province are abundant in this area. Precambrian rocks of the Owl Head mining district include the Pinal schist; gneiss; intrusions of granite, quartz monzonite and quartz diorite; and small amounts of Dripping Spring quartzite and metamorphosed Mescal limestone. These have been intruded by dikes and plugs of diorite and andesite, and are unconformably overlain by volcanic rocks and continental sedimentary rocks of Tertiary and Quaternary age. No rocks of the Paleozoic and Mesozoic eras have been recognized. The structural trends of the Owl Head mining district probably reflect four major lineament directions. The dominant structural trends found in the area are north and northwest. Subordinate to these directions are northeast and easterly trends. The strike of the northerly trend varies from due north to N30°E and was probably developed during the Mazatzal Revolution. The northwest trend has probably been superposed over the northerly trend at some later date. Copper mineralization is abundant in the area and prospecting by both individuals and mining companies has been extensive. To date no ore body of any magnitude has been found, but evidence suggests that an economic copper deposit may exist within the area. The copper mineralization visible at the surface consists mainly of the secondary copper minerals chrysocolla, malachite, azurite, and chalcocite with chrysocolla being by far the most abundant. Copper minerals are found to occur in all rocks older than middle Tertiary age. Placer magnetite deposits are found in the alluvial material of this area, and one such deposit is now being mined.

Previous mineralogical investigations (QemSCAN) performed on all effluent flotation streams of Mimosa mine (Zimbabwe) indicated the presence of appreciable amounts of platinum group minerals (PGMs), which are not recovered. Most, generally in excess of 70%, of the liberated PGMs in these streams belonged to the Pt-Pd-Bi-Te class in all the samples investigated. In the first part of this work, electrochemical investigations, electrochemically-controlled contact angle measurements and Raman spectroscopy have been employed to investigate the interaction of ethyl xanthate with Pd-Bi-Te and PtAs2. Impedance measurements showed lower capacitance values in solutions containing KEX indicating the formation of a continuous surface layer. Anodic and cathodic polarization diagrams show the mixed potential to be higher than the reversible potential of the xanthate-dixanthogen equilibrium reaction, hence the formation of dixanthogen on the surface is possible. Electrochemically controlled in situ Raman spectroscopy has confirmed the co-presence of xanthate with dixanthogen indicating that xanthate retains its molecular integrity when it adsorbs on the surface of the Pd-Bi-Te. The result of this investigation has shown dixanthogen to be present on both the minerals (PtAs2 and Pd-Bi-Te) when the surfaces are anodically polarized. Chemisorbed xanthate could be identified within 120 seconds yielding a hydrophobic surface as indicated by electrochemically-controlled contact angle measurements. Maximum contact angles of 63o were measured in the case Pd-Bi-Te. As a result the mineral surface is expected to be hydrophobic and a lack of collector interaction with the mineral is not the reason for low PGM recoveries experienced. Secondly, the flotation recovery of synthetically prepared Pd-Bi-Te was compared with that of chalcopyrite (a typical fast-floating mineral) and pyrrhotite (a typical slow-floating mineral), with microflotation tests. These indicated Pd-Bi-Te to be a fast-floater with flotation rates exceeding that of chalcopyrite. Predicted flotation rate constants (from the Ralston model) were significantly lower for small particles (with diameters similar to those lost to the effluent streams) compared with those of particle with intermediate sizes. This supports the suggestion that losses to effluent streams are caused by particle size effects. / Thesis (PhD (Metallurgical Engineering))--University of Pretoria, 2006. / Materials Science and Metallurgical Engineering / unrestricted

Nickel silicate laterite deposits developed on ultra-mafic rocks are similar in many general respects but they vary considerably in detail. The mineralogy of these surficial deposits is very complex and difficult to determine because of the fine grained nature and solid solution characteristics of the hydrous secondary minerals and because many of the phases are actually mineraloids that are poorly ordered or amorphous. To try some new approaches toward clarification of these phases, 24 samples from New Caledonia and Puerto Rico ranging from the ophiolite-ultramafic olivine-pyroxene-chromite-serpentine substrate rocks upward through intermediate phases of weathering to the final oxide -hydroxide iron cap phase were analyzed with the infrared spectrophotometer (IR -10) and with the automated X –ray diffractometer. Four limonite samples were also mineralogically analyzed. Goethite, secondary quartz, cryptomelane, hematite, chromite, talc, thuringite, and garnierite have been identified in various samples as weathering profile products.

The Big Horn Mountains are a geologically complex range that extends over 500 square km in west-central Arizona. Three major lithologic terranes outcrop: (1) Proterozoic amphibolite, phyllite, schists, gneiss, and granite; (2) Mesozoic monzonite to diorite intrusives; and (3) Cenozoic mafic to silicic volcanic rocks and clastic rocks. The entire area is in the upper plate of a detachment fault and, consequently, contains many low- to high-angle normal faults. Each lithologic terrane has its associated mineral occurrences. The Big Horn district is exclusively hosted in the pre- Tertiary terrane. Most of its mineral occurrences are spatially related to the Late Cretaceous intrusive rocks. One occurrence, the Pump Mine, may be a metamorphic secretion deposit, and therefore, would be middle Proterozoic. The vast majority of the mineral occurrences in the Big Horn Mountains are middle Tertiary in age and occur in three districts: the Tiger Wash barite - fluorite district; the Aguila manganese district; and the Osborne base and precious metal district. Fluid inclusions from Tiger Wash fluorite (T(h) 120 to 210° C, NaCl wt. equivalent 17 to 18 percent not corrected for CO₂) and nearby detachment - fault- hosted Harquahala district fluorite (T(h) 150 to 230° C., NaC1 wt. equivalent 15.5 to 20 percent not corrected for CO₂) suggest cooling and dilution of fluids as they are presumed to evolve from the detachment fault into the upper plate. Mass-balance calculations suggest that the proposed evolution of fluids is sufficient to account for the observed tonnage of barite and fluorite. The Tiger Wash occurrences grade directly into calcite- gangue-dominated manganese oxides of the Aguila district. A wide range of homogenization temperatures (T(h) 200 to 370° C.), an absence of CO₂ and low salinities (NaC1 wt. equivalent 1 to 2 percent) in the Aguila district calcite-hosted fluid inclusions argue for distillation of fluids during boiling or boiling of non saline-meteoric waters. Mass - balance calculations modeling the evolution of Ca and Mn during potassium metasomatism of plagioclase in basalt suggest that little if any influx of these cations is necessary to form the calcite –dominated manganese oxide tonnage observed. The Aguila district grades directly to the east into the base-metal and precious-metal occurrences of the Osborne district. Preliminary data describing geological settings, fluid inclusions, and geochemistry suggest that the Osborne district has a continuum between gold-rich to silver-rich epithermal occurrences. The gold-rich systems have dominantly quartz gangue, with or without fluorite, and are hosted in a variety of rocks, but are proximal to Precambrian phyllite or mid-Tertiary rhyolite. Fluid inclusions from two occurrences representative of the gold -rich systems spread across a minor range (T(h) 190 to 230° C., NaC1 wt. equivalent 17 to 23 percent not corrected for CO₂). Dilution of highly saline fluids is the inferred mechanism for precipitation of gold in the gold-quartz systems. The silver-rich systems have dominantly calcite gangue with or without quartz, and are hosted in mid-Tertiary basalt. Calcite fluid inclusions from a representative high-silver occurrence display a wide range of homogenization temperatures and salinities (T(h) 120 to 370° C., NaC1 wt. equivalent 7 to 23 percent). Boiling and consequent neutralization of acidic solutions is the inferred mechanism for the silver-rich, calcite gangue systems. A model inferring a regional fluid-flow regime and local sources of metals is proposed. Four possible regional and local causes of fluid flow in upper-plate detachment regimes are proposed: (1) regional elevation of geothermal gradients as a result of middle-crustal, lower-plate rocks rising to upper crustal levels; (2) meteoric water recharge along the southeast flank of the Harquahala antiform and consequent displacement of connate waters in the upper-plate of the Big Horn Mountains; (3) local emplacement of feeder stocks to rhyolitic flows; (4) and tilting of major upper-plate structural blocks.