Is there Gold in Northwest Connecticut?

The possibility of gold being found in northwestern Connecticut is much higher than most people think. The mineralogy of the older pre-Cambrian rocks that make up the core of the Northern Appalachians outcrops into areas within Litchfield County. These ancient rocks are found in several towns in the county in two different groups. One group includes the towns of Colebrook, Norfolk, Winsted and Torrington. The other group includes the towns of Cornwall, Goshen, Kent, and New Milford.

Bedrock of the Winsted, Connecticut Quadrangle.  The magnetite deposits are mainly found in the member marked Ygh.

Rocks of pre-Cambrian age that were laid down during the Grenville orogeny around 1.2 billion years ago crop out along the crest of the Appalachian Mountains reaching from Maine to Alabama where they all have one thing in common, and that is deposits of magnetite an oxide iron. It has been estimated by the Pennsylvania Geological Survey said the iron mines around Cornwall, Pennsylvania have produced an estimated 40,000 ounces of gold that is associated with the deposits of magnetite that are found in the area.

This illuminates a great deal of rock types that do not have to be searched for gold, rather it narrows the search to a particular type of mineral deposit namely magnetite. These deposits are easy to find because they create what are called magnetic highs on a specialized type of map called an Aeromagnetic Survey Map that are available at the DEP bookstore at 79 Elm St., Hartford, CT. There are several other good maps that are available from the same source. They also sell bedrock maps of all the quadrangles in the state. Another useful set of maps are the radioactivity maps that were done several years ago when the state of Connecticut performs a radiation anomaly map from the air.

All of the towns mentioned have at one time or another produced iron ore based on these deposits of magnetite. There were at least two of these mines in Winchester; the first one that was only active during the Revolutionary war was located at the top of Street Hill. The other mine was in the Danbury Quarter section of Winchester. But both of these mines produce about 50 tons over each, but from the records it appears they were never checked further gold content.

This is the kind of magnetite ore found around Winsted with abundant sulfides in the form of chalcopyrite.  The gold often occurs as thin film between the crystals of chalcopyrite.  Photo by Rob Lavinsky

The aeromagnetic map displays it extremely high anomaly right under Gilbert school that is strong enough to deflect a compass needle. There are several other areas in the town of Winchester that cause similar effects. One of these areas is right at the top of the borrow area for the Mad River Dam off old Route 44.

Gold deposits that are associated with granular magnetite tend to be low grade and disseminated through the rock is so little that it is normally not visible to the naked eye. The grade can be from grams per ton up to 4 ounces per ton. This is not bonanza ore, but the amount of ore that is available can be vast and capable of producing large amounts of gold.

This is not the type of gold prospecting where you are going to be able to find gold with the naked eye; instead all of these magnetic anomalies are going to have to be drilled, and the resulting cores are going to have to be carefully analyzed. This is not the kind of job that is normally undertaken by a single prospector instead it is going to require mounting an entire exploration team. Whether this ever happens the one thing you can be sure of this type of effort is going to cost several million dollars.

References:

If you want to learn more about gold mining and prospecting go HERE

Magnetite and Gold

History of Cornwall, PA

Bedrock Geological Map of Connecticut

The Author’s personal experiences