Thesis (Ph. D.)--University of Wisconsin--Madison, 1967. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

The central Florida, North Carolina, and central Tennessee phosphorite deposits account for 90% of the marketable phosphate produced in the United States. Scanning electrons and reflected light microscopy reveals that the iron-bearing minerals associated with these sedimentary phosphorites are related to the geologic setting and degree of weathering of the deposit. Pyrite and marcasite (FeS₂) are the principal iron mineral inclusions in unweathered phosphorites of Florida, North Carolina, and Tennessee, and occur as discrete, randomly disseminated microcrysts, irregularly shaped microcryst aggregates, cubes, dendrites, framboids, or bioturbation and interstitial pore space fillings. Pyrite and marcasite also fill the void spaces in skeletal phosphorites such as nerve canals in shark teeth of Florida and North Carolina and in bryozoan zooecium of Tennessee. The oxidizing conditions accompanying weathering in the terrigenous sand and clay environments of central Florida alter these inclusions to goethite (FeOOH), which occurs as pseudomorphs after the iron sulfides. However, hematite (Fe₂O₃) optically appears to be the iron sulfide pseudomorph in the phosphorites of the weathered carbonate environments in central Tennessee. The first reported occurrences of chalcopyrite (CuFeS₂), chromite (FeCr₂O₄), and an iron-potassium-silicate sheath surrounding some iron sulfide and iron oxides as inclusions in phosphorites, supergene ferrian-millisite [Ca₃(Al,Fe³⁺)₁₂(PO4)₈(OH)₁₈ • 6H₂O)] as coatings on phosphorites in the leached zone under a central Florida gossan, and secondary ferromanganese oxide spherulites as accessory minerals in Tennessee deposits are made in this study / M.S.

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.

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