Mining Operations at Mount Mica & Orchard Pit Mines, Oxford County, Maine.

Coromoto Minerals Mining Operations at Mount Mica,
September-December, 2008 Page 2 

2008 Oct-Dec Page 2

Our mining along this new drift had proven to be a setback for the ‘mined out faction’ (see page 1).  As I write this in 2012, I

Rene Dagenais (facing) and Dean McCrillis sitting in their  13m long huge but almost barren pocket of 1974.

can say by means of 20/20 retrospection the pegmatite was definitely not mined out. True, the character of the pegmatite had changed as we worked our way eastward but the frequency of  wonderments remained undiminished. Fascinating discoveries lie ahead of the work progressing in late 2008. I’ll attempt to continue to chronicle some of them here

In all candor pocket MMP20-08 was not a gem producer. Candor is a rare commodity as we all know. True, it had interesting smoky quartz with pink quartz rings but, after that, it was a bust. 20 was in the Dagenais pocket class. The Dagenais was a huge pocket found in 1974. Except for a few beryls and some quartz crystals there was little in it.  The tourmaline had suffered replacement. It was becoming more and more clear that we were indeed mining along the same trend that had produced the Dagenais. This line also produced the wonderful pocket of late 2004 (MMP28-04) that was very well endowed. The line is defined by a large fault in the country rock. The pegmatite thickens abruptly along this fault. This thickening is host to  concentrations of Li and Cs at regular intervals along its east-west trend.  Further along from 28-04 our huge pocket of 2005, MMP5-05, lay on this same trend. 5/5 was hybrid. Not as good as MMP28-04 in terms of tourmaline production but not has barren as the Dagenais or the most recent one, 20-08. In 20 we could plainly see the ‘should ofs’ and ‘could ofs’ in the form of gallons and gallons of epimorphs, casts, of mica after tourmaline. It seems if left to its own devices what tourmaline that develops in the pockets at Mt. Mica would like to eventually arrive at an endpoint in the form of muscovite. In the smaller pockets this process seems to be arrested before this disappointing outcome. Apparently 28-04 was just small enough to escape this destruction… if destruction is the correct term. Perhaps evolution is a better one.  28-04, as it turns out, was pristine. We opened it just a few weeks after starting to mine underground. We, sad to say,  didn't appreciate the rarity of this pocket. Perhaps we will find another like it in the future and savor it more.   

As we advanced our drift eastward beyond 20-08, we soon began to encounter massive Li minerals again. Fortunately for me it did not require an especially keen intellect to conclude that soon we’d encounter yet another large pocket. They seemed to be cropping up every 50’ or so along this fault.  The notion was beginning take root that the rewards in terms of gem production along this trend would be limited.  To either side, up dip (north) and down dip (south), the odds would tilt in the favor of the miners. We were now mining near to our drift of 2007 and down dip of it. For rock stability reasons we needed to determine where our current work was in relation to the 2007 effort. Drilling down from the upper drift with a slight down dip (southern) lean, we found there was a comfortable 13’ of rock between the floor of the upper drift and the roof of our current drift.  The drill bit emerged to the far left side of our ceiling and just above the area of 20-8. The point we chose to drill down was where we had found pocket 4-07. It had produced fine gem. This placed  4-07 just up dip of the near barren 20-8. In a similar relationship, our first big tourmaline pocket, opened in 2004, was just down dip of the disappointing Dagenais. The miners in the 70’s had probed the back of their huge pocket by drilling several holes in this direction. Their results were discouraging;  they abandoned the area. Without the aid of this critical intelligence, we aggressively mined the portion of the pegmatite they left with more than positive results.  Therefore, in my mind, I was starting to consider this heavy lifting work along the big pocket trend, with weak immediate prospects, to be investment. The real production would be to either side… or so it  is hoped. The cartoon above illustrates this notion. Pocket 20-8 is in the middle of the diagram. Pocket 4-07 sits just up dip of 20-8. By means of a time machine journey into the future, a gem bearing area is illustrated just down dip.


Map of the underground workings late 2008  Click for detailed map

Close up view of the area of MMP20-08

The fault and the related  thickening of the pegmatite is clearly seen in this image taken at the portal. Pocket 28-04 was 2m behind Mary.

Here Richard stands underground along the same fault 50m to the east of the portal. The structure and chemistry is little changed. Another big pocket, 1-09, is just 5m beyond Richard. Photo by Brian Pedersen.

The images above show the similarity in structure and chemistry of the pegmatite at the fault visible at the portal and the area of 20-8. The 20-8 area is more than 140' from the portal;  the structure appears the same.  Moderately barren pegmatite near the vertical face of the fault abruptly concentrating Li/Cs minerals 2 meters away. This pattern continues to hold into current mining (2012-time machine again).  Careful recording of our mining and plotting features on our map allows us to draw 3 more observations. (1) Each large pocket has with it an associated lepidolite mass.(2)  In each case  the mass is on the western end of the pocket. (3)There also appears to be a rough proportionality between the size of the Li mass and the volume of the pocket. The bigger the lepidolite the larger the pocket.

As hinted above,the mining eastward in late November and into December started to show the first signs of another large pocket. However, like 20-08, this pocket also appeared to have undergone extensive replacement. In the image to the right the continuation of the fault can be clearly seen along with the appearance of lepidolite to the left. Also, all of the component parts were there.  To the left elbaite sprays are precipitated in mica books. This is always a good sign and is one of the 50+ infallible pocket indicators. However,  the early  vugs we found  were in pretty bad shape. Hence, our expectations were not great. Mining this area was also not a cake walk in winter. It was the lowest part of the mine. The cold air would settle here and so would the water. To work it required near constant pumping. However, being the stalwarts that we were(are), we pressed on.  


The early vugs looked pretty grim

...but this nearby large schorl going to elbaite is a good sign. It is very similar to the one in the wall at the portal. That particular one shows up all over the Internet. No credit is given to the miners who left it there for show and tell...


In this image a 2mx1m microcline is capped by lepidolite

Brian stands in the sump hole cum working face. Microclines are clearly visible on the left

We would not begin to appreciate the magnitude of the space we had just encountered start until much later. We did not return to this area until 2011. The difficulties of mining at the lowest point in the mine in the dead of winter turned our January '09 mining up dip. This area, though a pocket, would better serve us as a temporary sump hole. In fact, in 2012 we would test the notion that better pockets lie down dip of the big ones (and up dip too).( In 2012 we'd mining just under Brian's feet but in the wall.) The lower ones we call the 'root'. This is based on the notion that the first areas to crystallize around a big space are down dip where the pegmatite at Mount Mica is thinner.  Blue Sheppard , the operator of the Stewart Lithia Mine, refers to the up dip pockets as chimneys. If I have his notion right, the concept is the same I

Trying to stay warm and dry as we struggled to work the latest pocket