THE IMPACT OF PHYSICAL AND CHEMICAL WEATHERING ON IRON SLAG FROM STANDISH, NY

From 1883 to 1907, magnetite ore was smelted at a facility located in Standish, NY. Standish is located in the northeastern region of the Adirondacks. The industrial processing at this site left behind a pile of slag that covers ~13 acres of land. The slag at the site has been classified into 6 broad types based on their physical properties. Exemplars of select types were studied to characterize the impact of physical and chemical weathering on their appearance and bulk chemistry.

The impact of weathering is clearly evident through a comparison of samples collected ~15 years ago to partner samples still out in the field which are more pervasively fractured and coated with calcitic weathering rinds. For more quantitative data on the impact of weathering, we carried out a field experiment and a leaching test. The field experiment entailed exposing different slag samples (glassy, chalky, and massive) from Standish to rain and monitoring the changes in mass over an 8 week period. Each of the three textures lost mass however, the greatest loss came from the glassy sample (1.3% lost). Water that had interacted with the samples was collected. All of the water samples contained particulates and also produced a precipitate from evaporation. This multi-week experiment indicated that both chemical and physical weathering play a role at Standish, but to better understand the role of chemical degradation, we carried out a simple acid leaching test using 2M nitric acid on four samples. All samples lost mass and left particulates in the remaining solution. Bulk chemistry of pre and post test samples was determined by XRF. The chemistry of Standish slag is dominated by SiO₂, CaO, and Fe₂O_3(t). A highly vesicular slag showed the largest changes in chemistry (including Ba, V, Zn, Sr, Zr, and Ce) and also changed the pH the most. The other samples showed changes in major elements as well as in Ba, Sr, and Zr.