Bristol Copper Mine, Bristol, Hartford Co., Connecticut, USA
|Latitude & Longitude (WGS84):||41° 43' 9'' North , 72° 55' 26'' West|
|Latitude & Longitude (decimal):||41.71917,-72.92389|
|Köppen climate type:||Dfa : Hot-summer humid continental climate|
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, mainly in the late 1840s (to the consternation of some operators) and are in many museum and private collections. Bateman (1923) provides a good summary:
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):
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.
Jones (2001) provides perspective on the famous specimens:
These miners reportedly found the Bristol orebody to be reminiscent of those at Truro, Redruth and Penzance, Cornwall. In the late 1840’s the “Cousin Jacks” would be on hand for the discovery of vugs lined with crystallized chalcocite, and may have troubled to preserve many specimens. Dr. Steven Chamberlain of Syracuse, New York, has reported that when he visited numerous private collections in Cornwall, England, over a hundred years later, “he observed, unexpectedly, a number of fine Bristol chalcocites which had been assigned a Cornwall pedigree,” apparently brought or sent home by Cornish miners (Heitner and Lininger, 1997)...
In 1847...Major stockholders included Yale people such as John M. Woolsey, Josiah D. Whitney, and Professor Benjamin Silliman, Jr. - son of Benjamin Silliman, Sr., the great mineralogist who “almost single-handedly took Yale into pre-eminence in early American education in chemistry, geology and mineralogy” (Moore, 1999). This connection with the Sillimans of Yale would prove fortuitous for Bristol and its great mineral specimens.
The position of mine manager went to 24-year-old Charles Moore Wheatley. Although already a successful businessman, Wheatley had only an amateur naturalist’s interest in geology and mineralogy, and no experience in mine management. However, his quick intelligence, enthusiasm, hard work, and dedication to mineralogy soon won him the support and respect of Benjamin Silliman, Jr. The warm relationship would pay continuing dividends for the Peabody Collection at Yale when Wheatley later took charge of the lead mines at Phoenixville, Pennsylvania, which now bear his name, and sent many fine specimens from there to Silliman in New Haven. Unfortunately, his tenure at Bristol lasted only until 1849, when he left to work at the Perkiomen and Ecton mines in Pennsylvania (Evans, 1984).
Under the leadership of its new cadre, the Bristol mine flourished, and soon was rated the most important copper mine in the northeastern United States (Smith and Smith, 1907)...
Many of the historically important specimens now in the Yale-Peabody collection certainly came to light at this time. A large number of fine chalcocite specimens also went to Union College, which is not surprising considering that Eliphalet Nott was president of that institution while also heading the Bristol Mining Company in the late 1840’s. Many more fine chalcocites also went to Union College in 1858, when Charley Wheatley sold his collection to the school, Josiah Whitney having arranged the sale...
The 1850’s saw a major disagreement among the owners and managers of the mine about what to do with the fine crystal specimens being found. Most of the owners wanted the specimens simply sent to the stamp mill to increase the yield, but Silliman (?) objected strongly. Hurlbert (1897), describing the management of the mine during 1855-1857, writes “It was during this administration that specimens of chalcocite of peculiar form could have been easily sold as cabinet specimens for hundreds of dollars, [but] were crushed for ore in spite of the protest of the mineralogist.” Heitner and Lininger (1997) speculate that this “mineralogist” was Benjamin Silliman, Jr., or possibly Josiah Whitney or Ludwig Stadtmüller. It was perhaps in part to protest the fate of these specimens that Silliman and Whitney sold out their holdings at the same time as did Nott - in 1857. Their reason also may have been the financial extravagance of Henry R. Sheldon, hired in 1851 as mine manager and bringing with him a Cornishman, Captain Williams, to oversee the property and production.
Commodity ListThis is a list of exploitable or exploited mineral commodities recorded at this locality.
23 valid minerals.
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
201.3 - 252.17 Ma
|Mesozoic volcanic and intrusive rocks|
Age: Triassic (201.3 - 252.17 Ma)
Comments: Connecticut Valley Basin
Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. 
458.4 - 470 Ma
|Sweetheart Mountain Member [of Collinsville Formation]|
Age: Middle Ordovician (458.4 - 470 Ma)
Stratigraphic Name: Sweetheart Mountain Member
Description: Gray and silvery (not rusty), medium- to coarse-grained, poorly layered schist, composed of quartz, oligoclase, biotite, muscovite, and garnet, and in places kyanite or sillimanite. Amphibolite layers common; also layers of quartz-spessartine rock (coticule). In the Bristol quad., CT, Collinsville Formation is revised to include a basal unnamed hornblende gneiss member (was upper part of Stanley's (1964) Bristol Member), a middle unnamed metaquartzite member, and the upper Sweetheart Mountain Member. Bristol Member of Stanley (1964) is raised in rank to Bristol Gneiss in the report area. Collinsville unconformably underlies The Straits Schist. Inferred age is Middle Ordovician (Simpson, 1990).
Comments: Part of Central Lowlands; Iapetus (Oceanic) Terrane - Connecticut Valley Synclinorium; Gneiss Dome Belt, Hawley Formation and equivalent formations (includes Collinsville Formation) (Middle Ordovician). Secondary unit description per CT008.
Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052.