Tuesday, April 19, 2016

The Carroll Mine in Carroll County, Maryland

The Carroll Mine was one  the four largest 19th Century copper and iron mining operations to exploit Carroll County, Maryland’s Sykesville Mining District. Worked intermittently between the 1840's and 1880, it appears to have received the least attention over the years from the mineralogy community. The copper and iron  bearing species from all four major mines in the District  were much the same. Cobalt-bearing  Linnaeite Group species occurred at all four mines, though not in sufficient quantity for successful commercial production. 
We are grateful to Stuart Herring, a prominent Baltimore-based collector and dealer, whose research led us to the several pits and grown over dumps from these Carroll Mine workings. While trails lead to the only other two mining areas that still exist in the Sykesville Mining District, a substantial bushwhack is necessary to reach the mostly grown over remains from the Carroll Mine.

The Carroll Mine hosted two separate operations at different time periods. Though primarily a producer of iron, at least one shaft was worked for copper by the New Burra Company. The material on the surface around the pits and near the dumps varies. Specular hematite and magnetite are quite easy to find.  Near one of the shafts, most likely the Burra Shaft, are sizable chunks of crystallized epidote, stressed massive garnet, and magnetite. All three host an abundance of copper bearing minerals.


Magnetite---ore quality:

Bornite---ore quality.

Chysocolla is abundant amidst the copper bearing minerals and ranges in color from a pale blue-green to a vivid medium blue.

Lesser quantities of malachite sometimes accompany the chrysocolla, often in small green crystal sheaths.

Chalcanthite and melanterite appear to the naked eye as earthy pale blue crusts hinting at  microscopic crystals, The crystallization becomes clearly evident under the scope. The two species can often be difficult to visually distinguish from each other.

Pyrite and chalcopyrite were present, but not as prevalent as at the Springfield and Mineral Hill Mines. We did not find any cobalt bearing linnaieite-siegenite-carrollite material .

Although native gold has not been reported from the Carroll Mine dumps, we kept our eyes peeled for it. Throughout the area was a fair amount of  white quartz that was weathered in a distinctive manner.  It visually  resembled quartz that once yielded a few  gold particles at an isolated nearby pit, long since built over. .