Friday, September 25, 2009

The Discovery of Ore Hill

The Discovery of the Ore Hill Mine:

One summer afternoon Ezekiel Ashley and John Pell climbed a small hill on a 100 acre tract of land they were surveying in the Town of Salisbury Connecticut. At the top of the hill they discovered soil that looked exactly like iron rust. That was exactly what it was, hydrous iron oxide, more commonly known as “limonite” an ore of iron. In 1887 the decedents of Ezekiel Ashley were still proprietors of the mine on Ore Hill.

At first the local blacksmiths came to the mine and hauled the ore off in their saddlebags where they refined it into wrought iron at their forge. This is a way of smelting iron ore directly into iron by causing the ore to be reduced to iron by removing the oxygen in the ore by combining it with charcoal. This process makes a spongy mass of iron and slag that afterwards is hammered on an anvil. This process called louping causes the impurities to be driven from the iron. The result is a bar of wrought iron ready to be used for other articles made of iron.

The first furnace capable of making cast iron was erected seven miles away in Ancram, NY by Phillip Livingstone. This furnace was to take an active part in the Revolution as it was this furnace that forged one of the chains that George Washington caused to block the Hudson River at West Point.

We can thank nature for this wonderful ore, but we have to look into the dim past over four hundred years ago when there was a volcanic arc of islands similar to modern Japan that in the process of erupting caused a layer of volcanic ash to rain down on top of the vast coral reefs along the east coast of North America. This was called the Walloomsac formation. Between eruptions the coral reef laid down another thin layer of limestone that then would be buried by the next eruption. This created a formation that was a layer of volcanic ash interbedded with a limestone. The result was a calcareous schist that was rich in iron and magnesium.

Both iron and magnesium are capable of acting as a weak acid under the right conditions. The right conditions were met by the underlying limestone reef. Over years this calcium carbonate extracted both iron and magnesium from the Walloomsac formation. The remarkable iron ore found on Ore Hill was one result of this chemical magic, another was the replacement of some of the calcium in the limestone leaving a new rock called Dolostone.

The combination of iron ore and Dolostone was just what the doctor ordered. One was the ore, and when it was added to the iron furnace the Dolostone acted as a flux making the ore easier to smelt using charcoal.