|Mining Operations at Mount Mica & Orchard Pit Mines, Oxford County, Maine.|
|As October came to close
the weather was changing fast. Though it would not last all day,
we were often greeted in the morning by a thin film of ice that had
developed on the sections of our bench that weeped water. By this time
we had extended our cut to the eastern or upstike end of the main pit.
This is the point at which both Merrill in the 1890s and Plumbago in
the 1990s had decided to quit in this area of the pegmatite. Merrill
then decided to open a new pit just east of the main one.
According to Hamlin ( History of Mount Mica)
,they began this cut at the site of the original 1820 discovery and
mined in southeastward direction. In this new pit, in 1904, Merrill
opened the largest pocket found at Mount Mica to that time . Over
100 years later
Plumbago followed Merrill's lead and began working in this new pit as
well. Our approach though would be a little different. Our game
plan, as laid out from the beginning, was to continue advancing our cut
eastward. We would be essentially merging the main pit into the eastern
one. We would then continue advancing the pit still furhter eastward
until the mineralization played out. Frank Perham, when he worked
Mica in the 1960s, started from the upstrike end of the secondary pit
and worked westward. He did not encounter elbaite until he got to
within yards of the 1904 pocket. Our hope is, that as we work
through this area further down dip, our luck will be better. In fact,
hope the elbaite zone will continue even farther east into the Irish
Pit. As written previously, C. Hurlbut, Jr, a geologist from
Harvard, in a 1953 article in the 'American Mineralogist', Beryl at Mount Mica, Maine,
proposed that the Mount Mica pocket zone may indeed extend into and
beneath these far workings. Based on Hurlbut's map on page 752, Perham
may have been unsuccessful on the far eastern end of his workings
because the pocket zone had been eroded away in that area. The
pegmatite does in fact tilt up in the easterly direction and in fact
extends to the surface. This contrasts sharply with the image above
where 30 feet of schist sits above the pegmatite. ( click to see maps)
Each area of the pegmatite, at least in our experience, seems to have a slightly different macro composition. For example, coincident with finding the pockets with light blue elbaite, we were finding abundant löllingite, FeAs2, either mixed in with the cleavelandite of the garnet line or filling fractures. The pink tourmaline seemed to be associated with areas of massive lepidolite. As we reached the eastern end of the main pit, beryls, which were encountered sporadically before, were now densely packed within the cleavelandite band above the garnet. These beryls, some quite large, were either pale green or blue. Many had gemmy eyes. Lore has it that Merrill felt that beryl was a contra indicator for elbaite. Based on our experience we would expect another change in the elbaite as we mine through this area.
In the image above three distinct levels of the pit floor can be noted from left to right. The left most level, in places near vertical, are the remnants of Merrill's work. The central level is the portion mined by Plumbago. Our workings are, of course, the lower right most level. The dip of the pegmatite as well as a pronounced hump can be seen. The hump gives the impression that the pegmatite to the right is plunging. What really seems to be the case is the pegmatite has thickened in this area and returns on the right to the more typical 10-12' of vertical height. As previously noted, this thickened area seemed to be relatively poorly mineralized. This state of affairs may have been what led Merrill to abandon this end of the pit and move his working eastward. Plumbago on the other hand interpreted the right hand drop of the pegmatite as a plunge. The last of their cut is just to the left of the white rod in the picture. What we found is that it is not a plunge and as the pegmatite thinned out, the mineralization improved. MMP25-05 (pocket 25 of 2004), one of the largest we encountered in this end of the pit, occurred just as the pegmatite thinning occurred. (see image at the right).
By the beginning of November we had to abandon our excavation eastward as the forming ice was making it too hazardous to stand on the ledge. We had few options other than attempt starting a shallow adit ( tunnel) in the down dip face. Interestingly, in the upstrike and down dip corner of our workings, the mineralization had intensified. A densely packed group of downward radiating schorls sat above a thickened band of cleavelandite with a few wisps of lepidolite mixed in. 20 feet to the right was the zone of massive lepidolite, spodumene crystals and pollucite. Near the schorls we found a small vug filled with golden cookeite that teased us to continue by producing a few matchsticks of aqua colored elbaite. Richard and I had received our MSHA required 40 hours of training from an MSHA certified instructor and we had the basic tools required to get started with the work. We decided to commence our adit in the area in between these two zones. It looked poorly mineralized and would be a low risk area to start the burn cut. The burn, a closely spaced series of holes that are heavily loaded with explosives, is the means by which an advance is started. Anything within the burn is completely pulverized. As we drilled our burn pattern, we were surprised to see the drill cuttings coming out pink . There was so much color that a pink dune was developing from the water used in drilling. ( Underground work necessitates the use of water with the drill to suppress dust.) Once we had completed the burn and widen the adit to it's full width and height we could see a thick band of lepidolite in each of the side walls and in the back as well. Lepidolite rimmed mica books were embedded in the cleavelandite. Heretofore, we had only seen rimmed mica books in the proximity of a pocket. At this point we were only in 4 feet. Our next advance was 6 feet. We placed our burn this time well above the rich zone of mineralization. After completing this round we were now in 10 feet. As I was hoeing the muck off of the top of the mineralized zone, a piece of cleavelandite peeled away exposing a small dark opening. We had found a small pocket. Although no bigger that a cantaloupe, the pocket contained several pieces of blue elbaite. We were pleased not only in that we found a pocket but that we had managed to do so without damaging any of its contents. In the image to the left notice the mass of schorl near the pocket that is illuminated by the lamp. Richard is holding up a blue elbaite section.
Encouraged by our limited success, we decided to make another 6 foot advance. With the aide of a drill template to space the burn cut, we were becoming more efficient driving our adit. We could now make the advance in 2 days of steady work. The process involved removing the upper part of the pegmatite to within a foot or so of the mineralized zone . With the top removed, we could then drill under the garnet line by similar distance and using light charges loosen the material that might contain a pocket. This time though we noticed immediately when we removed the upper part of the pegmatite during the 3rd advance ( 15' in), that the back face of the adit was riddled with rusty fractures. We had last seen such a density of cracks around pockets MMP7-04 and MMP11-04, the large ones that yielded quantities of green elbaite. Without saying it , Richard and I were thinking the same thing. Could we be heading to a large pocket of aqua colored elbaite? Soon we would have to suspend the mining as I need to go to Germany to attend a medical trade show. We hastily drilled a series of holes to lift up the mineralized zone. After these holes were shot and the mucking completed, we got down to the task of examining what we did or did not find. The mineralized zone continued to look promising but we had exposed no pocket. After several hours of fruitless chipping and prying, dejection started to set in. Almost as an afterthought, I stuck a chisel into one of the bootlegs on the right side of the back wall of the adit. ( A bootleg is the bottom of a drill hole that remains after the blast. Its is usually only a few inches deep). The chisel didn't do much. As I pulled it out, Richard noticed a trickle of water coming from the hole. I repeated the process and we observed that the flow increased and did not seem to abate. We repeated this process several more times and each time the flow increased slightly. We continued chipping on the back wall but it did not yield. At this point, it was getting dark so we would have to resume the hunt the next day. We were both convinced that something was back there.
The next morning we were surprised to see a large pool of water covering the floor of the adit. Heretofore our adit had been dry. I decided to pump this water out into two 5 gallon pails. After one was filled, we would switch to the 2nd one and empty the first. By so doing, we counted 60 buckets of water before the adit was dry. This process gave us a good idea of the minimum size of the space hidden somewhere beyond our sight. It was at least 300 gallons or nearly six 55 gallon drums. Not bad, but where was it.? We decided to drill a few 4 foot holes in the vicinity of the hole that was still draining water. Immediately the drill went into a small space. We were able to drill some adjacent holes that did not encounter a void. We loaded a couple of these and shot them lightly. After removing the muck from this small blast, we were able to put our hands into a small void. The space contained small gemmy smoky quartz crystals and some white opaque elbaite. This space was, generously, no larger that a bushel basket. As we dug this cavity the flow continued unabated. We knew we were not in the main portion of the pocket. After a lot of digging with small tools and our now raw fingertips, we were out of time. Furhter exploration would have to wait until I returned from Germany at the beginning of December. We worried the weather, which was already quite cold, would put an abrupt end to our plans until Spring.
Opaque white elbaite