Bristol Copper Mine, Bristol, Hartford Co., Connecticut, USA

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A copper mine situated on the western border fault of the central Connecticut Mesozoic Hartford Basin. Commercial mining began in 1837 and carried on intermittently until 1953. World class specimens of chalcocite and bornite were saved (to the consternation of some operators) and are in many museum and private collections. Bateman (1923) provides a good summary:

"The mine lies at an elevation of 350 feet near the northern line of the town of Bristol, Connecticut, and about four miles from its center. It is on the contact between the red Triassic sandstone of the Farmington River Valley and the crystalline rocks of the western upland. The former gives rise to a flattish topography and the latter is bordered by a line of rolling hills, here and there marked by steep faces, which in the vicinity of the mine rise to an elevation of 650 feet."

"In the earlier part of the nineteenth century the State of Connecticut boasted of a number of mines, and the Bristol mine ranked first among the copper properties. It is reported to have been discovered in 1836 and was first described by Shepard in 1837. Mention was also made of it by Percival in 1842.

"Prior to 1847 it was worked in a desultory way and there was shipped to England about 125 tons of high-grade ore. From 1847 to 1853 it was more vigorously worked. During this period some half million dollars was spent upon the property; workings were extended to a depth of 240 feet and to a maximum distance of 500 feet along the vein and 120 feet across.

"During this same period, nearly $200,000 was obtained from about 2,200 tons of picked ore with an average copper content of 33 per cent. Some time after this the mine was closed. It was again opened in 1888 and a new shaft was sunk in the sandstone to a depth of 378 feet. Levels were run to depths of 30, 40, 50, and 60 fathoms, respectively, each one of which traversed the sandstones lying between the shaft and the contact, and penetrated into the schists...The mill was rebuilt and considerable mining activity took place until 1895 since which time the property has been idle. There are data available as to the amount of copper that was produced during this period, but several thousand tons of tailings on the dumps indicate a considerable extraction of ore.

"The principal opening of the mine is a large pit some 100 feet or so in diameter, which represents a portion of the mine that has caved in. It is now filled by water. Two working shafts are visible. One is 125 feet from the schist-sandstone contact in the sandstone, and is said to be 240 feet deep. The other shaft lies 225 feet further eastward in the sandstone area, and is 378 feet deep...None of the workings are accessible at the present time. Another shaft, said to be 100 feet deep lies some 500 feet to the south. In addition to the main open cut, old prospect holes, shafts, and tunnels may be seen to the northeast, along what is presumably the contact. Everything is now covered with vegetation so that little can be seen."

Afterward the mine was idle for decades with one last attempt in 1947-1953 as summarized by Jones (2001):

"The world wars had brought on copper shortages and high copper prices, and Allen Hearst of Forestville, Connecticut, convinced himself, both that there were still significant ore reserves in the Bristol mine, and that 20th-century technology could profitably extract copper even from low-grade ores at Bristol.

"Hearst formed the Connecticut Mining and Milling Company with the express purpose of extracting silver and copper from the tailings on the site. He also undertook some limited dewatering and building. But the fall of world copper prices from their wartime highs finally saw to it that the venture was not successful; the mine was abandoned again in 1953. The property, zoned for industrial use, is now leased by a fuel oil company with a portion of the property used for a rubble dump and equipment storage site. The shafts have been filled and sealed, and access to the underground workings of the deposit will probably never again be possible."

Mineral List

Allophane Azurite Baryte 'Biotite' Bornite Calcite Chalcocite

Chalcopyrite var: Blister Copper Chrysocolla Copper ? Covellite Cuprite Digenite

Djurleite Dolomite Galena Malachite Molybdenite Muscovite Pyrite

Quartz Siderite Silver Sphalerite Tenorite 'Tourmaline'

27 entries listed. 24 valid minerals.

References

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