The 2001 Season at the Orchard Mine
Track Drill Provides Clues - November 2001
If you have plowed through the 2001 pages to this point you know I have
worried about what was ahead as we exposed more of the Orchard Pegmatite.
Since September of 2000 and for 60' along strike, the pegmatite has been
not generous. Only in the Fall of this year has it begun to hint
at better things to come. Heretofore, and since almost the very beginning
of our efforts at the OP, we have had to contend with 20-30' of schist
country rock sitting on top of the ' good stuff '. As we mined eastward
this schist mantle thickened as the coarse grain zone of the pegmatite
shrank along it's vertical dimension. Interestingly, except for a brief
stretch , the width of the pegmatite has been remarkably consistent at
16-17 feet. If the schist were to continue to thicken the pegmatite
would be history or as they say ' pinched out '.
Our approach to mining the Orchard involved benching down through the schist for 20' or so along strike. Then we worked the mineralized zone until it graded down into a fine grain feldspar. This worked well in the beginning. However, as we mined eastward we were faced with a taller and taller headwall. This presented some technical challenges. As we would finish a cycle, the pit would be nearly empty and the headwall about 60' high. As the next cycle began, we could muck off the first 10-15 feet of bench down the headwall by reaching down with the excavator arm. This process was not for the feint hearted operator as the perception was that the cab would follow the arm down into the abyss. Reaching down we could only push muck off. Digging with the bucket was too hazardous. So once upper 15' of bench had been cleaned, the next 20' or so was out of reach of our excavator from either above or below. This middle 20' had to be cleaned by back power. Uncooperative large fragments known locally as ' pianoes ' had to be barred off the ledge or pulled down by cables attached to the excavator. The cabling was hazardous as well. The trick was for the excavator to be back far enough from the cascading piano and for the ' cable man' , me, not to become part of the slide. In addition to the risk factor, the effort required to reach the mineralized zone was escalating.
As can be seen in September page, the pegmatite appears to have been pushed out of it's neat little crack in the country rock by a huge mass of schist. Eastward the pegmatite been injected into a well defined crack. Early work on this eastward portion of the pegmatite exposed lots of quartz and very massive microcline crystals to 1 meter. But how deep was it? Was it just 20' sitting on top of schist or did it continue downward for many more feet? These were questions that for me begged answers.
Our solution to getting a peek into the rock below was to bring in a track drill. In the 60's the Bureau of Mines had conducted a survey titled ' New England Beryllium Investigations '. A core taken at the Orchard, east of where we were working at the back of the upper pit shown in the photo at the left, indicated only 25' of pegmatite. Core drilling could again be done but the cost was in the neighborhood of $35/foot. We opted instead for a low tech look at the drill cuttings a simple boring operation would bring up. The price for a bore hole would average only $4/foot. ' Maine Drilling and Blasting' was contracted to do this work. In one day we able to drill more than a dozen holes to a depth of 60 feet in various locations of interest around our mineral lease. In the photo at the top of the page
piles of white cutting are visible. The pile at the left foreground was
from hole 'A' placed on the northern contact about 20' east of the headwall.
(See the diagram at the bottom of the page). Hole 'A' was bored to 60 feet
encountering only pegmatite and no country rock. At 40 feet a pocket was
entered which gushed up water, microclines and quartz crystals. Besides
the color and texture of the cuttings, the penetration rate , sometimes
as fast as 3 meters/minute, gave a clue to the nature of the rock below.
The coarsest grain was penetrated at the fastest speeds, the country rock
at the slowest. Holes placed further to the right and up strike encountered
pegmatite consistent with the increasing dip of the vein. It was apparent
from this informal look that the Orchard had not pinched up strike for
at least another 75 feet. The western end of the pegmatite was a different
story. We could find no pegmatite in the cuttings from bore holes placed
at the mouth of the pit.
So thus encouraged, the unusually warm weather this December allowed us yet one more session. Our mining strategy has changed somewhat. We now intend to work the pegmatite all the way to the back of the current exposure in cuts of about 20 feet. We have let the muck accumulate in the pit so that the excavator is able to reach the top of the headwall from within the pit. When we reach the back we will return to the front of the cut, muck out another 20 feet, and repeat the process. Working at the top of the peg, we were struck as to how coarse the grain has become. Initially work in coarse zone produced few beryls. Now we were finding many blue beryls in quartz filled spaces between the large microclines and along the borders with the intermediate zone.
In November rose quartz was beginning to appear within the large masses
of quartz about 15 feet below the top of the pegmatite. Now this rose had
become quite deep in color and gemmy as well. We saved every piece of this
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