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Geology Articles » Salisbury Iron Ore - Early Iron Industry of Connecticut
The Salisbury Iron Ore and
The Early Iron Industry of Connecticut
by John Carter © 2007
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Limonite Bog Ore
Photo by Tomasz Kuran
GNU Free Document License
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There are six different iron ores found in minable quantities in Connecticut. Each of these ores has been used to produce iron or steel at one time or another. Whether the iron was produced in a Catalan forge or a blast furnace depended on the skill of the iron makers. There were a number of processes that dealt with the iron after it was refined; these included slitting and rolling mills, foundries, steel mills, forges and other processes. A review of Connecticut iron ores is provided below.
Bog Ore
This was man’s first iron ore used for thousands of years before America was settled. It is an impure hydrous-oxide of iron that precipitates from iron rich ground water upon entering anoxic bogs. It was first documented as an iron ore in North Haven, and spawned the first iron furnace in Connecticut. This blast furnace was built at the outlet of Lake Saltonstall in East Haven by John Winthrop the Younger in 1651 and it remained active until 1678 when apparently the ore beds were exhausted. Bog ore also supplied many of the small forges throughout the central and eastern part of the state.
Magnetite Sand
Although magnetite sand is commonly found as a heavy mineral in the beds of streams, in Connecticut it more commonly found on the beaches of Long Island Sound, eastwards from New Haven into Rhode Island. One is able to make this ore into iron in a forge, but in the case of magnetite sands they were more useful as a blotter for ink.
Massive Magnetite
Massive magnetite is associated with the Precambrian rocks of western Connecticut. It was mined in Cornwall Bridge and the Tuttle mine in Winsted. Both of these mines produced around fifty tons of ore each. Earlier during the 1770’s it was reported that there was a magnetite mine on Street Hill overlooking the town. Also in Winsted, a very high magnetic anomaly exists right under the Gilbert High School that although not investigated may be another magnetite deposit.
Sharon Quadrangle - Geologic Map of Connecticut by John Rogers and Others.
Available online at tmsc.org
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The Salisbury Ore - Limonite
The ores that were designated Salisbury Iron didn’t all come from Salisbury, Connecticut. They are in the Walloomsac formation with deposits of the same kind of ore that are scattered across several states. Aside from Connecticut they were also mined in Vermont, Massachusetts and New York. The ore bodies extend from Vermont to Manhattan, NY. The Walloomsac formation extends under southern Manhattan and one might as well say that Wall St. has an iron foundation as the as the Walloomsac formation extends under Wall Street.
The ore itself is mostly the goethite variety of limonite making it similar to bog ore, but it is far more dense. In Salisbury itself it is found on Ore Hill. Today all that remains of the open pit mines are two water filled pits. One of these pits is right alongside Rt. 44 half way between Lakeville, CT and Millerton, NY. It is no longer active although during World War II it was pumped dry with intentions to reopen it, but the war ended, and the pit refilled with water.
The Roxbury Ores
These ores are much different then any of the others found in Connecticut. Rather then being composed of iron oxide these ores are iron carbonate, siderite. Siderite comes from the Greek word sideros for iron. Siderite is roughly the equivalent of calcite with iron substituting for calcium. Siderite and calcite form similar crystal habits; only siderite is denser. Some specimens show an iridescence that is caused when the mineral oxidizes. This oxidation product is goethite.
Conclusion
All of these ores are easily smelted into iron in either forges or blast furnaces. In the case of siderite, iron made from it is easily turned into steel. For over 200 years Connecticut supplied most of the United States with its iron needs. It wasn’t until the iron industry moved west to Pennsylvania that Connecticut lost its position as a major iron provider.
Reference
Merguerian, Charles; and Moss, C. J., 2006, Structural Implications of Walloomsac and Hartland Rocks Displayed by Borings in Southern Manhattan.
Available online as a .pdf document.
Article submitted by John Carter, 27 Greenwoods Garden, PO Box 282, Winsted, CT 06098, 860-248-9987 (cell), 860-238-7073 (land), geotekllc@netscape.net.
Biographical Note: I came into geology later in life then most geologists. The first 18 years of my working life was as an experimental machinist or a process engineer. I left this profession behind me in 1967, and for the next 12 years I was a commercial helicopter pilot. During this period I also earned my geology degrees. I couldn’t completely escape my early profession because after getting my degrees in geology I went into the environmental consulting business until I retired. At least this knowledge allowed me to know where the skeletons were buried, and who buried them. I still put in more then 8 hours a day on my latest reincarnation as a writer and photographer. I am single having been divorced for several years, and have no children. |
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