USGS/RONALD A. SLOTO

Figure 1. The cast house encloses the furnace at Hopewell Furnace National Historic Site. The stone stack of the furnace is visible on the left side of the cast house. In the foreground, part of the furnace slag pile is exposed and makes up the left bank of French Creek.

The U.S. Geological Survey (USGS) is conducting research at Hopewell Furnace National Historic Site (fig. 1, above; also see sidebar) in southeastern Pennsylvania to determine the fate of trace metals, such as arsenic, cobalt, and lead, released into the environment during the iron-smelting process. Arsenic is a carcinogen, cobalt is a suspected carcinogen, and lead can cause severe health problems.

Iron ore containing elevated quantities of trace metals was smelted at Hopewell Furnace during its 113 years of operation (1771–1883). The ore used at Hopewell Furnace was obtained from local mines, mainly the Jones and Hopewell mines, which were within 5 miles (8 km) of the furnace. The iron ore deposits were formed during the early Jurassic period about 200 million years ago. The deposits are mineralogically similar and contain abundant magnetite, the chief iron mineral, and accessory minerals enriched in arsenic, cobalt, copper, and other metals.