SLAG FROM STANDISH, NY-A BOON OR A BANE?

Standish, NY is the site of a once highly active iron smelter that produced vast quantities of slag from the mid 1800's through the early 1900's. Almost 100 years later, this slag still persists in what is the largest pile of slag in the Adirondacks. This pile, visible in aerial photographs, covers more than an acre of land and in some places exceeds 60 feet in height. The slag in this pile is a reminder of the metallurgical history of the Adirondacks and might also be a treasure trove of inexpensive aggregate, but it also is a point source for contaminants and has issues with slope stability.

The Standish slag pile is comprised of a variety of slag that ranges in composition from 100% glass to a glass-crystalline mixture where 70% is crystalline. The most predominant mineral in all of the slag is gehlenite. In addition to gehlenite, traces of calcite, fayalite, charcoal, and metallic iron are present. Though these minerals don't seem to be of environmental concern, the average bulk chemistry of the slag indicates otherwise. Samples show enrichment in Ba, Sr, Y, Zr, and in some cases Nb (with some of these elements present in 100's of ppm's).

The contaminant potential of the Standish slag pile is directly linked to the chemical resistance of the slag. Close study indicates that some of the slag is acutely prone to weathering -- some having been reduced to nothing but a fine powder in less than 100 years. The formation of this powder is primarily due to chemical weathering not mechanical pulverization. In addition, a weathering crust of sulfur and calcite is pervasive throughout the pile. This crust coats exposed surfaces and also is found lining cracks of large samples and within vesicles.

The weathering of Standish slag (which is rapid in some cases) releases contaminants into the surroundings. It also decreases the mechanical strength of the slag, indicating it might be ill suited as road fill. The slag at this site is certainly important as a technological artifact, but it is associated with engineering and environmental problems that must be addressed.