| Slag is the waste formed when ore is smelted to extract a metal. This research investigated the mineralogy, chemistry, and alteration of slag and has forged new pathways in the world of slag research by using multiple geological and analytical tools. These tools include simple hand sample observations, traditional light microscopy, X-ray diffraction, X-ray fluorescence, and electron microscopy (electron microprobe and transmission electron microscopy).; Knowledge of slag mineralogy, chemistry, and alteration is necessary to predict if a slag will release hazardous elements into groundwater, surface water, or soil. This is especially a concern when slags contain radioactive elements or heavy metals. This research concentrated upon the mineralogy, chemistry, and alteration of tin slag from southwest Great Britain and from sites in Pennsylvania monitored by the United States Nuclear Regulatory Commission (NRC). The mineralogy of these slags was not uniform, and there were few similarities between the British and the American samples.; British tin slags formed from two different smelting processes (blast furnace or reverberatory furnace) are distinct mineralogically and chemically. Also, many of the slags from Cornwall are radioactive. In all of the British slag fragments, glass and iron prills are the most susceptible to alteration.; Studies of the slag from the NRC sites yielded different information. Samples of hibonite from one of the slags were studied with transmission electron microscopy in order to investigate their atomic structure. The hibonite crystals were practically defect-free, although one crystal featured a second nanoscale phase within its structure. The interface between this phase and the hibonite was coherent.; Another NRC slag contained Cr-rich spinel. Further studies of this slag indicated that dendritic periclase and metallic iron prills were highly susceptible to alteration and were replaced by Fe-oxyhydroxides at the sample's edges. An estimated weathering rate for this slag is 7 μm of slag per year. An estimate of the maximum release rate for U and Th from the slag is 2.4 ng/cm 2year. A complete understanding of the mineralogy, composition, and alteration features of all slags is essential for determining their long-term safety and stability. |
