By Dan May
On Our Land
Dan May
Mining is a minor industry in Connecticut today. There are about 75 active mining sites statewide, all surface workings. Crushed stone, sand and gravel are the main raw materials produced, along with minor amounts of clay and architectural dimension stone.
Historically, though, Connecticut has a rich and diverse mining history, dating to early colonial times when copper was first mined at the Old New-Gate Mine. Historic operations also recovered other metals including silver, gold, lead, tungsten, cobalt, iron and even uranium.
More than 1,000 inactive mine sites can be found across the state, and two metal mines once operated in West Haven. One documented site was a lead and silver mine located at Maltby Lakes around 1820. This was a small mine, with hand-dug shafts about 10 to 20 feet deep chasing small flakes of metallic ore in a quartz vein into the bedrock. The pits have since been covered over by the construction of the reservoirs there.
Prospecting for gold in quartz veins also was intermittently active until the 1930s at Phipps Lake, near the train station. This site even had a minor gold rush during the Great Depression.
I am not sure how potential ore was located in forested New England in those early days, but I am familiar with modern prospecting. My first geological job was as a field assistant for the Branch of Mineral Resources in the US Geological Survey. I worked on a project assessing the resource potential of tribal lands of the Tohono O’odham Nation in southern Arizona. This is one of the largest tracts of tribal land in the US, encompassing an area about the size of the entire state of Connecticut. It is located southwest of the rich copper and gold belts of central Arizona, and tribal leaders engaged the USGS to see if the tribe might strike it rich, too.
Exploring a region starts with a simple approach – sampling river sand and gravel from the major watersheds and analyzing their mineralogy and chemistry to see if they have elevated levels of desired metals. A high level indicates that rocks somewhere up in the watershed contain ore minerals with those metals that are being eroded and carried away by streams.
Once an anomaly is detected, it can be traced upstream progressively through branching tributaries until a potential bedrock source area is identified and targeted on-ground mapping can begin. We did not find any high-grade metallic ores for the tribe that are mineable at current price points, but other resources were identified.
That first job taught me how much you can learn from a jar of sand. For years I awarded extra credit to geology students if they brought me a jar back from their excursions at fall or spring break, and if I could not reasonably identify whether it was a beach, river or dune sand as well as where it was from geographically. Sometimes they made it easy (bright white quartz sand in a rum bottle), but I rarely had to give full points as extra credit.
My first exposure to Connecticut came when I was teaching in Ohio and a student brought me a micaceous sand full of oyster shell and metamorphic rock fragments. Her face fell when I deduced it was from a Long Island beach, and she told me it was from a place called Milford Point. She was a great student and earned an A anyway.
River sands and even beach sands record the geology of the source rocks that provide the sand in the first place, especially when not far removed from that source rock. Connecticut beach sands are distinctive, and few (with a little training) would confuse a beach sand from Silver Sands State Park with that from Hammonasset State Park.
However, I was stumped last year on a field trip down the Cove River from Maltby Lakes past Phipps Lake to Bradley Point when we got to the shoreline there. We did not find any gold or silver ore flakes, but instead found a very exotic sand, unlike any I have seen regionally and certainly not what was to be expected coming out of the Cove River. It did not even look like sands dredged out of deeper parts of Long Island Sound that are used to replenish eroding beaches. Some of the students took up the challenge to find the sand’s source. They learned that it had been imported from Cape Cod to replenish the beach after the major storms accompanying hurricanes Irene and Sandy. And thus, they wanted to go prospecting at Cape Cod, too.
Dan May is a geologist.