The Mine Hill blast furnace in Roxbury, the best-preserved relic of Connecticut's once-thriving iron mining and refining industry.

There was only one major iron mine east of Cameron's Line, the Mine Hill iron mine in Roxbury. A different sort of deposit was worked at Roxbury and, perhaps not coincidentally, it proved to be one of the least successful iron mining ventures in Connecticut. The mineral that occurs in Mine Hill is siderite, a carbonate of iron. It was worked in underground tunnels and required a more complicated process than limonite ore to refine to pure iron. Although the iron mining and manufacturing at Roxbury proved a dismal failure and operated for only five years (1867 to 1872), its furnace has survived the tests of time and vandals and is the best-preserved furnace in the state.

One of the most significant effects of the iron industry on the land was the widespread deforestation it caused. Huge amounts of charcoal were required to keep the furnaces "in blast," fostering a support industry that employed many men and horses to cut, haul, and char the vast timber stands of the Northwest Highlands. The hunger for charcoal motivated loggers to tackle even the steepest of slopes, and there is hardly an acre in the northwest that went uncut. Scattered throughout the region are the remains of thousands of pits where the wood was converted to charcoal. But advances in iron smelting technology (for example, the switch from charcoal to coal) and the discovery of the huge iron ranges in Minnesota and Wisconsin tolled the end of Connecticut's iron and associated charcoal industries. The fires of the last operating blast furnace, the Beckley furnace in East Canaan, were extinguished in 1923. Today, the woods have recovered - not to the grandeur of the original forest, but to such a verdant extent that it is difficult to believe that the plateaus of the Northwest Highlands once stood bare.

Unlike iron mining, quartz mining still continues in Connecticut. The only operating mine is the Lantern Hill Mine in the southeastern Connecticut town of North Stonington. Lantern Hill itself is high enough that it can be seen from Long Island Sound eight miles away. The name "Lantern Hill" comes from its former use as a landmark for ships plying the coast. During whaling days, bonfires were often set blazing on the hilltop so that ships returning at night could locate their home ports.

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