Friday, November 25, 2011

Mining the Christine Marie: The Nature of the Deposit

The first vein of Morrisonite Jasper
When I got the dozer down the last hill to the flat area where the road comes up from the river, I had only a couple hundred yards of level road to make before I would be in the deposit. It did not take me very long to get the dozer over there and I did not do a very good job on building the road either.        
As I was pushing loose rock to the right down the slope, I hit a big solid rock in the hill on the left side of the dozer. I worked around the rock with the dozer and then stopped to take a look at it. Much to my surprise I could see a vein of jasper running down the side of the rock. The vein was about 2 inches wide at its widest point and narrowed down to nothing on both ends. It was about 2 feet long and had a well defined egg pattern through most of it. I worked on the jasper in the large rock for several days digging around the big rock and chiseled and hammered to remove the jasper under the big rock I discovered more small broken rock with no jasper in it.
The mine at its deepest. The top 1/3 of the mine contains the float.
                When I first hit this rock with the dozer blade I thought that I had hit a protruding piece of host rock. That is to say that I had found the deposit and would now be able to follow the jasper into the hill from one rock to another. This was not the case. There was no jasper to be found around the big rock. The large rock was a float rock just like the little small rocks around it. The deposit had to be deeper into and up the hill from this rock which had moved down from above to its present position.
                All the jasper bearing rock on the hillside on the south end of the Christine Marie is fractured and moved. The deposit is as if a gigantic mass of rock was shattered, cracked, and then pushed slightly to separate all the pieces but not enough to mix them up. The top of the deposit is mixed up and is a steep slope containing all sizes of rocks. It is falling down over itself and small pieces of jasper can be found anywhere on the slope. The deposit excavation I made into the hill was about 20 feet below the original surface. Here the rocks were bigger- one ton or more in size but still stacked on top of each other with cracks between them sometimes 8-12 inches wide. The float, or mixed up rock on top, was 5 to 10 feet thick.

An early shot of the mine. notice all the cracked rocks.
The interesting and very unusual thing is that the cracking in the host rock has nothing to do with the cracking that allowed the jasper to form. The jasper must have been formed at an earlier time when the welded tuff was not shattered as it is today. While mining it is possible to follow the jasper in one rock to another rock even though the two rocks have been moved apart from each other. The jasper on the Christine Marie, unlike the jasper on the Jake’s Place claim, is held very tightly to the host rock. On the Jake’s Place claim the host rock is easily broken away from the jasper and most of the jasper follows cracks in the host rock. On the Christine Marie the welded tuff must be broken off the jasper with considerable effort, and it is rare for the jasper to be found in a natural crack. This means that the mining requires a lot more hammer work. On the plus side, the severe cracking in the host rock makes finding the jasper bearing rocks relatively easy. This is a very good thing because of the scarcity of the jasper in the deposit.
Notice how the jasper jumps from rock to rock without any relationship to the surrounding rocks.

Friday, November 11, 2011

Mining the Christine Marie: Watching a Rock Fall

Rocks fall onto mountain roads all the time, but rarely do people see it happen. Trees fall in the forest when the wind blows hard, but it is unusual for a person to be in the right place at the right time to witness it. The more I worked into the steep slopes of the Christine Marie claim, the more I knew when a rock slide was about to happen.
Big rock ready to fall.

I was following small veins of jasper in small rocks down around a very large rock. The large rock, about ten tons in size, did not have any visible jasper showing in it. The large rock was nested in among a vast number of smaller shattered rocks that did have some jasper. The large rock had moved here from some place higher up the slope. I worked slowly down the side of the rock over a period of several days, exposing it as I went down. The jasper I was finding was good, but small. The seams were barely ¾ inch wide, and did not go very far but traveled from one rock to the next as I worked down. I finally found the bottom of the large rock which seemed to be standing on its end, and the jasper in the small rock started to show indication of getting better. I started to follow the jasper under the big rock.
Rock in the upper left before the fall.
After working for a while, I got up to take a break and look things over. A little to my surprise the big rock looked a little more precarious than it had earlier. It was hanging in the back wall of the pit with not a lot of other rocks holding it in place. I thought it would be fun to watch the rock fall by itself. I went back to work, more carefully this time, removing rocks from under and around the large rock, one at a time. After a while I started to hear small noises coming from around and under the rock. I got out of the hole I was working in, found a nice rock to sit on far enough away to be safe, and watched and waited.
The whole process took about thirty minutes. Every few minutes there would be a creaking sound or a small pebble would slide down the slope under the rock. Then, there would be a long silence before another sound or trickle of dirt would cascade down the slope somewhere else. After another long silence, I became impatient and tossed a small stone below the big rock. At first the sounds and movement increased in intensity but then it went back to their natural rhythm.
The rock after the fall.

Finally, after about thirty minutes the sounds and rock slides under the big rock rapidly increased and the large rock fell over on its side as if someone gently pushed it over. It was fascinating to watch the whole process and realize that the rocks on this slope are continually falling; some just faster than others.