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Post by Bob on Oct 25, 2021 14:04:25 GMT -5
Since I spend a lot of time around Lake Superior, I don't regard puddingstone as uncommon. Most of the pieces I see that are small enough to carry are not completely solid and have voids and bad places showing, so I generally don't pick it up. Last year, I found a gorgeous piece but estimate it weighed about 300lbs so passed on that!
My notes shows that a few years ago, when I was studying rock classification and reading a lot of minerology and petrology books, that this material is a sedimentary rock, and it is "quartzite with jasper embedded in it" and mostly occurs in Ontario.
Does anyone who knows a lot about it think that's a fair definition?
It is true that it's mostly a Great Lake region material?
Can the matrix be pretty dark? My reason for asking is I have discovered that a rather dark rock I've polished looks a lot like it, but I don't think it came from that area.
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Post by rmf on Oct 26, 2021 7:52:40 GMT -5
Bob I have not read anything on it but I assume MI Puddingstone was sedimentary but has had some regional metamorphism since it is a quartzite not a sandstone. Similar to Baraboo WI area quartzite. As for puddingstone in general there are various types (pebble conglomerate). TN, Al, Ark, MS all share a formation of puddingstone but it is made of chert and cemented by a limonite, geothite,hematite silt. So you get a white to brown in a black-dark brown back ground. SD has a jasper conglomerate from the Lakota fm and it has reads and purples in it. MI conglomerate is really the only "puddingstone" that actually looks like the puddingstone it is named after.
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Post by Bob on Oct 26, 2021 9:23:32 GMT -5
...MI conglomerate is really the only "puddingstone" that actually looks like the puddingstone it is named after. Huh? I had no idea what you are talking about. I just looked it up on Wiki. Had no idea there was all that info available, including that it might be a rather common material in several places on this continent. Christmas pudding isn't something I've heard of, so looked it up also. Now I know why it was named so. Sure enough, found a few images of Christmas pudding sliced that has the look of puddingstone I've seen from time to time with that lighter colored matrix.
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Post by Bob on Oct 26, 2021 9:24:18 GMT -5
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Post by Bob on Oct 26, 2021 9:32:02 GMT -5
That's the rock. I have no idea if this is puddingstone, or just some resilicified brecciated jasper or what. This is the only rock quite like this I've ever found. It took about a year to process. When I got it shaped up in rough grind, there were holes all over it and I wasn't optimistic. It spent quite a bit of time in 220 working on the holes. This is after burnish after two weeks in alum ox. The surface doesn't meet my usual criteria to keep, because parts of it are still kind of lousy, but I'm kind of attached to this rock which is unique for me. Although I don't think they made it in the closeup, a few of the breccia are green and translucent like little gems.
Although you can see a lot in these photos, if this rock was 10' away and you just glanced at it, it would just look dark brown. It really is pretty dark overall.
Oddly, coming out of 1,000 grit, there were almost no holes anywhere, and the rock had a nice satiny, smooth finish. But in polish, it sort of went bad and holes opened for some reason, but the solid pieces in it did polish and the colors popped much more coming out polish than 1,000.
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Post by hummingbirdstones on Oct 26, 2021 10:15:12 GMT -5
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Post by rockjunquie on Oct 26, 2021 10:22:29 GMT -5
Puddingstone is just a named conglomerate from the Michigan area. There are others with different names or just called conglomerates. Puddingstones seem to be the best looking, IMHO.
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Post by Jugglerguy on Oct 26, 2021 15:38:18 GMT -5
That's a conglomerate, but it doesn't look like a typical Michigan puddingstone. In my experience, there are not many puddingstones in Lake Superior. I have found two, both in the eastern U.P. near Point Iroquoise Lighthouse. I mistakenly have called them sedimentary rocks in my videos, but they're actually metamorphic, having been sedimentary before that.
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Post by Bob on Nov 3, 2021 17:35:34 GMT -5
I had seem some photos of the ones with the light matrix like that, but that's wonderful, striking photo of many of them. Actually, I think those are kind of ugly, though not sure entirely why I react that way--not referring to these polished rocks per se, but just the general look of this conglomerate polished or not. The ones I've seen with a matrix that light are somewhere east of Grand Marais, MI, and somewhere near Pancake Bay PP, Ont. I guess it makes sense if the definition holds that the matrix is quartzite that they would mostly look like those. Most of those I've seen have a brown matrix, even if not near as dark as the rock I photo'd in this thread. Apparently I need to stop calling them puddingstone and just refer to them as conglomerate. I've been trying hard to remember where I have seen rather large ones, that are up above the water in the high storm thrown line of the beach. That might have been much further to the east at the edge of Killarney PP. It was before I was into rocks and backpacking along the beach and remember seeing this unusual look. I think my hiking buddy called them Frankenstein rocks.
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Post by Jugglerguy on Nov 4, 2021 22:55:43 GMT -5
I had seem some photos of the ones with the light matrix like that, but that's wonderful, striking photo of many of them. Actually, I think those are kind of ugly, though not sure entirely why I react that way--not referring to these polished rocks per se, but just the general look of this conglomerate polished or not. The ones I've seen with a matrix that light are somewhere east of Grand Marais, MI, and somewhere near Pancake Bay PP, Ont. I guess it makes sense if the definition holds that the matrix is quartzite that they would mostly look like those. Most of those I've seen have a brown matrix, even if not near as dark as the rock I photo'd in this thread. Apparently I need to stop calling them puddingstone and just refer to them as conglomerate. I've been trying hard to remember where I have seen rather large ones, that are up above the water in the high storm thrown line of the beach. That might have been much further to the east at the edge of Killarney PP. It was before I was into rocks and backpacking along the beach and remember seeing this unusual look. I think my hiking buddy called them Frankenstein rocks. There are other conglomerates that are also referred to as puddingstones. I used to think that they just looked like concrete and didn't like them much either. Actually, I still think they look like concrete, but a better, natural version. They have grown on me.
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Post by Bob on Nov 28, 2021 21:45:37 GMT -5
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