The Carroll Mine in Carroll County, Maryland

The Carroll Mine was one  the four largest 19^th 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. .

John White and a Rock Pile

Actually we  were trespassing as we peered through a pile of rocks dumped just a few feet off a lonely country road in York County, Pennsylvania near Delta. John White and I  had  tried unsuccessfully to locate the landowner. In the process, we learned that the a local power company had dumped the rocks there in conjunction with a project that never happened. Hopefully, the landowner wouldn't mind.

John had expressed interest in these rocks over the past year and had encouraged me to check them out. He had described the material as "just serpentine rock."  For reasons that hindsight now renders lame,  I had not yet done so. What was wrong with me? When a past Curator-in-Charge of the national mineral collection who also founded Mineralogical Record gets excited about a site less than an hour's drive away, it's worth a look.

Then last week, John emailed me an invite to see some of the rocks he'd purchased at the recent Denver show. Attached was the image shown at left. It pictures cabs from material John had found when he first discovered the aforementioned rock pile last year.  His email suggested that after looking at his Denver acquisitions, we drive there.

We did and ended up crawling over the pile of serpentinite rocks. There were numerous pieces worthy of John's cabs. Antigorite was abundant, especially  the columnar picrolite variety. Colors ranged from  very light green to very dark green. Gemmy coatings of medium to dark green  antigorite occasionally comprised the rocks' surfaces. This antigorite was slightly translucent, but less so than antigorite (var.) williamsite.  It also lacked those chromite spots so definitive of williamsite. The  rock beneath the antigorite was grainy, dull greenish gray and black, possibly chrome-bearing, and iron-bearing almost for sure. Though we didn't have magnets, John had learned  when the cabs from his earlier find were made  that much of the black material here was magnetic.

One specimen that particularly interested me is the quartz (var.) prase shown at right. Is presence along with the serpentinite strongly suggests that the rocks on this pile were from the neighboring Cedar Hill or Penn-Maryland Quarries just a few miles east in Lancaster Couty at Fulton Township. Both quarries exploit the same kind of serpentinite rock that's part of the Baltimore Mafic Complex.

 Another piece that impressed me features an intersection of massive magnetite with pale green antigorite (var.) picrolite. Were it chromite rather than magnetite meeting that picrolite, I suspect some williamsite would be gracing the picture as well. Assuming that the rocks originated at either the Cedar Hill or Penn- Maryland Quarries, such a find would seem reasonable. Chromite as well as magnetite is known to occur at both localities

All told, we spent less than an hour at the rock pile. We departed because we were hungry and still marginally clean enough to be served a hearty lunch at a family restaurant a few miles away.

 Thereafter, we continued about ten miles further on  to check out ---with permission---the edges of another rock pile that John knew about. It consisted mostly of  "Wissahickon schist."  We quickly uncovered some graphite, pyrite, and siderite.  This was a much bigger pile of rocks. Unfortunately,  later commitments limited the amount of time we had to see as much of it as we would have liked. Stay tuned.