Geology/Identify a rock
Can you help me identify this rock I found? I live in Asheville NC. I was walking and looked down and saw it. It was such an odd rock. It fits in my palm. Hoe can I sen you a picture of it. It look a like a fossil.
Okay, first, Asheville is an interesting place for geology. It is pretty complex. I used to have an old girlfriend who's family was from that area, last name was Knipe. She was one of two identical twins, and used to know how to clog.
Okay, back to geology. From what I can see in the photos you sent me, it looks like you have a rounded clast of quartz which may be chert. Chert is a very fine grained quartz and includes flint, chalcedony and others. It looks like it is brecciated, which means it was fractured and then recemented back together by injection of hydrothermal fluids bearing dissolved quartz that filled thr fractures cementing the pieces back together.
Now considering the geology of the Asheville area, that all fits. The Appalachian mountains are a very old chain of mountains that at one time rivaled the Himilayas in size and height. That was when they were young. Now they are old and eroded and all we see are the stumps the remains of the once high peaks and their roots. The Appalachians were formed by a collision between the North American plate and the African Plate. In fact, the Appalachians are the western part of a range of mountains that formed and the Atlas Mountains in Morocco along the north western coast of Africa are a continuation of the Appalachians. Think of them as the dented fender on the other car after two cars collided, the crumpled fender of the second car are the Appalachians. Continental drift caused the collision and them separated them. Simialr rocks and fossils exist in both ranges and is how we correlated, or matched them up.
Now the rock you have is metamorphic rock,as are most of the rocks in the Asheville area. They consist of layers of sedimentary rock, rocks formed in water by the layering of sand and mud and gravel, and volcanic rock, laid down as lava flows, and ash. All these rocks were being deposited along the east coast of North America but were eroding from mountains way up in Canada and the sand and gravels were being transported to the coast by long extinct rivers.
A modern comparison would be the rivers moving sand and muds thorugh China and dumping them into the East China sea. The rivers are flowing from as far away as Tibet and these would be that same as the long ago eroded mountains of Eastern Canada. This was all being dumped into an ocean between Africa and North America.
Then as continental drift occurred, the ocean closed and the two continents collide.The sands, muds and gravels had formed sandstones, shales and conglomerates and the bulldozing continents mash them together changing them by metamorphism, by the great pressure and temperatures generated. This is when the breccia was formed, the silt or fine sandstone was squeezed and the minerals recrystallied, it fractured and hot quartz containing fluids were forced in and recemented the rock.
The over millions of years it weatherd out, and was transported by a stream or river bouncing along as the sharp angular edges were rounded off and it was finally deposited again in the place you found it, which may have been lithified into another rock, or deposited in a stream or river gravel deposit where you found it.
Now it could have been dug up by a road construction crew and transported and depostied as fill for a trail or something, but in a nut shell that is how it formed.
Asheville sits in an area where several layers of the old ocean basin are now turned up on edge. Think of a stack of throw rugs laid on top of one another. Each rug is a different rock, sand, ash, basalt, shale. Now if you push the rug from the ends making it rise in wrinkles. Those wrinkles and folds would be the Appalachian mountains when they were young.
Now if you could take a big knife and cut the wrinkles off about an inch or two from the bottom, that would be the mountains today and the ends of the layers sticking up would be how the rock layers would be laid out if you walked across the surface of the ground west to east through the Asheville area. You would pass over northeast southwest trending bands of different rocks, layers of metamorphosed volcanic rock, sedimentary rock etc. This just happens to be the general trend of the mountains too, because some erode easier and form valleys and other do not and they form the ridges. I am from the Shenandoah Valley up in Virginai which is an extension of the same trend, only up there, the metamorphism was not as great.
Now back to the modern example of China. Off shore of the East coast,there was a chain of volcanic mountain islands similar to Japan and as the continents closed all those rocks got jumbled in the mix and account for the volcanics mixed in of which there are a lot in the Asheville area.
So suffice to say you have a metamorphic rock, probably a fine siltstone, or maybe even a
metamoprphosed carbonate, a kind of marble. Take a steel nail and see if it will scratch the rock. If it is soft it is possibly a metamorphosed carbonate. If it is hard and glass won't scratch it, its quartz and a metamorphosed siltstone or quartzite. Quarzite is a sandstone that has been squeezed and heated to the point that the individual sand grains had dissolved into one another, erasing evidence of the individual grains, at least to the naked eye.
The rock was then fractured and recemented when super hot fluids bearing dissolved quartz was forced into the cracks cooled and precipitated the quartz in the veins, cementing it together again. All this happend while it was deeply buried and the mountains were going up due to the collision.
Attach it to the form, last page just before you approve sending. Click the link that says "Attach an Image". The path to where the picture is on your computer, then select it and click okay. Or you can send it to me at keithhpatton at hotmail dot com.