MINERALOGICAL ANALYSIS OF IRON SLAG FROM STANDISH, NY

In the mid to late 1800’s and into the early 1900’s, Standish, NY was the site of the world’s largest catalan forge which extracted iron from the local Adirondack ores. Over the course of almost 100 years of industrial activity, this forge left behind a large 60 ft tall pile of slag, a byproduct of the smelting processes. The pile covers ~13 acres of land in the Adirondacks. This research aimed to better understand the variety of phases present at the site as well as products associated with weathering. Though there are a variety of slag types found in the Standish slag pile, all are chemically dominated by CaO and SiO₂. Powder X-ray diffraction (XRD) of numerous samples from Standish indicate that there is phase homogeneity throughout the site and that materials like glass, gehlenite, pseudowollastonite, and quartz dominate the unweathered material. Pure iron prills are also present in many of the Standish slags. When the iron prills are exposed to air, they quickly oxidize. In some highly eroded and fissile slag samples, calcite is an additional phase. Many samples at the site are coated with a layer of white powder that is composed of a mixture of Ca-rich phases such as bassanite (2CaSO₄•H₂O) and kottenheimite (Ca₃Si(SO₄)₂(OH)₆•12H₂O). XRD analyses of slag samples exposed to laboratory leaching experiments with nitric acid indicate that calcite is the dominant phase lost in multiple samples. Overall, the breakdown of the Ca-silicates as well as the oxidization of iron dominates the weathered products at the site.