by John Carter on 21/08/09 at 8:59 am
This is a description of a gold and cobalt deposit in Cobalt, Connecticut.
There is a cobalt – nickel mine located in the village of Cobalt a part of East Haddam, Connecticut. This mine was in operation from the time of the Revolution in the 1770s until 1855 producing cobalt and nickel from an arsenide that contained of both metals. There were a succession of mining companies who operated the mine digging many shafts and adits. They even erected a mill to refine the ore which was mostly shipped overseas to China where it was used as an enamel for porcelain to make the blue images found on fine china.
The history of mining in this area goes back in time even further to the time of John Winthrop Jr. as the first governor of Connecticut. He is reported to have mined gold in the same area as the cobalt mine, and cast rings from the gold. No one knows how much gold he discovered because he kept this knowledge to himself. The author read a story how the governor’s rings were the basis of J.R. Tolkien’s “Lord of the Rings” series. The area where the cobalt mine is used to be called the “Governor’s Ring” because it is thought that it was in this area that he found the gold for his rings.
It is part of a state forest where in the 1980s Prof. Anthony Philpotts and his class of budding geologists discovered one of the richest gold lodes ever discovered in North America. This was in an area of Silurian aged quartzite which was assayed by the United States Geological Survey, USGS, and from samples of the quartzite they were able to extract from 1.5 to 6 ounces of gold per ton from the quartzite.
When this area was being mined for cobalt the miners sank their shaft right through this bed of quartzite to reach the cobalt ore. They had no idea that the gold was there at the time. Prof. Philpotts and his students went to examine the old cobalt mining operations and were flabbergasted to find the gold in the overlying quartzite.
The place where the cobalt was discovered was in the Bronson Hill Anticlinorium that was an Ordovician age Island Arc very much like modern island arcs that originated off the coast of the North American Craton that had an east dipping subduction zone and a sea between the volcanic arc looking like modern Japan. This island arc was eventually collided with the North American Craton during the mid-Ordovician Taconic Orogeny. At this time it was incorporated into the craton, and there it has remained since.
To see a similar situation no one has to look further then Ontario and Quebec where the Abitibi greenstone belt hosts many mines for both precious and base metals. It is supposed by Canadian geologists that this feature was caused by the collision of one or more island arcs with the Archean craton.
During the Silurian era when a wave washed beach formed on the sea side of this island arc the action of the waves worked on a sand beach concentrating the gold into a Placer deposit of gold that now resides in the quartzite formation. It is interesting that this or similar quartzite can be traced into western New Hampshire.
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