E&ES 109 Geology of Connecticut
Fall 2002 J. Gregory McHone
Cobalt, Gold (and Arsenic) in East Hampton
Adapted from text by Prof. Jelle de Boer
John Winthrop, Governor of Connecticut, was reputed to have found gold near Great Hill sometime around 1660. According to former Yale president Stiles, Winthrop used to resort in the woods of this mountain (Great Hill) roasting and assaying metals, and casting gold rings (diary, 1787). One of the rings was supposedly presented to the King of England. In 1762 Dr. John Sebastian Stephauney and several men made a horizontal opening into the side of the Chatham stream. The men were probably looking for gold, but found cobalt. Eventually, the old reports of gold in the area were taken to be more myth than reality.
The name Cobalt comes from the German word Kobold, or mischievous imps, that roamed the German Black Forest. They took special delight in getting mortals to pursue the earth's riches and greatly suffer as a consequence. The silvery ore, which when treated produces an evil odor reminded the Germans of the riches sought by these gremlins to tempt the mortals. After presumably having problems with financing, Stephauney returned eight years later with two Dutchmen. Chatham records indicate that one of these (Erkelens) leased land for mining in 1777. In 1787, Erkelens left for China with twenty tons of cobalt, after he had failed to sell this treasure to the porcelain factories in Delft (Holland). When cobalt ore is refined, it yields the deep blue pigment known as "cobalt blue," which was used extensively in the 18th and 19th centuries in Chinaware and glassware. Erkelens must have been quite an entrepreneur because he also erected a distillery. Fields suggested that the purpose of starting this enterprise was "to supply his workmen more conveniently with a beverage, which they loved and to supply exposed and suffering soldiers, who could hardly be expected to live and fight bravely without the aid and stimulation of strong drink."
The presence of gold in this area was not confirmed in the 18th and 19th centuries, despite relatively extensive exploration and mining for cobalt and nickel between 1762 and 1855. In 1986, geologists from the University of Connecticut were sawing through an ore specimen found in the area and discovered a yellowish coating on their saw blade, which was gold that had smeared off the sample being cut. This exciting find soon made headlines and a miniature "goldrush" developed in local and national newspapers. The gold location is on private land not far to the west of the Cobalt mines, but it appears to be too small a deposit to warrant a new mine.
The gold and cobalt-nickel minerals of cobalt occur in mineralized zones a few tens of meters apart on either side of an E-W trending fault zone. The gold occurs along with pyrite and native bismuth in small fractures within quartz-arsenopyrite veins that are several feet wide. Pyrite (an iron sulfide) is also known as "fools gold". No wonder that earlier miners and geologists had difficulty recognizing the real gold.
Questions: Given that the cobalt is mixed with arsenic in sulfide minerals, what environmental problems might result from indiscriminate dumping of the mine wastes? After visiting this old mine, do you see any special safety problems here, or are the present fencing and signs satisfactory?