brizzonator
off to a rocking start
Member since July 2020
Posts: 23
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Post by brizzonator on Oct 12, 2020 11:46:50 GMT -5
Hello, most of my rockhounding for tumbling material is in the creeks and rivers here in SE Texas, in particular the west fork of the San Jacinto.
Because of that, almost all my finds are at least lightly smoothed. On occasion, one is so highly tumbled that I only want to give it a final polishing(such as this bracciated agate that I found, about 2-3 inches long), but I'm a n00b and am wondering where in the process I should start(and if I am polishing a lighter volume of these stones, should I then put in ceramic media).
I have a single tumbler (I just got another to raise the volume I can process, but have not used it yet and is still a tumbler) and my normal process (which has seemed to give decent results): *8 days @ 60 grit *8 days @ 180/220 *10 @ 500 *1-2 hour with liquid soap *7 days @ 1200 aluminum oxide Thanks!!
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lordsorril
freely admits to licking rocks
Member since April 2020
Posts: 866
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Post by lordsorril on Oct 14, 2020 18:56:45 GMT -5
There is a difference between shaping and polishing. The question is: Which one do you want to do? Shaping usually involves Silicon Carbide grit and polishing is usually successively increasingly finer grades of Aluminum Oxide grit. 1200 Aluminum Oxide is generally considered more of a pre-polish than a true polishing grade grit. If you are looking for suggestions to proceed with tumbling the rock pictured--then it is really subjective. If it was me: and the rock is small (around quarter size)--I would leave it in coarse grit until I ground down some of those pits. If the rock was larger (a few inches)--I would cleave it with a rock chisel on the indent on the left, and then straight down on the large pit on the right to get a smoother edge rather than waste the time/energy/effort trying to grind out those features. Anyhow, just my two cents.
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Post by pauls on Oct 14, 2020 23:12:08 GMT -5
Start at the start, yeah really. Even the smoothest seeming river or beach rock has significant subsurface damage from bashing around in the current. It probably wont take long to just remove enough of the outer layer to get to good solid rock though.
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Post by Bob on Oct 15, 2020 9:07:11 GMT -5
That rock is very much like what I find in a certain formation a few hundred miles from you to the NW. So much so that I bet it's from same ancient underground gravel bed. I have tumbled a lot of it. It's not easy and out of 100 pieces, maybe 10-15 come out well. It would be a terrible material to learn start on. Just FYI, and sorry too.
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Post by Bob on Oct 15, 2020 11:52:54 GMT -5
It doesn't hold up well in many cases to the pounding of normal rough grind, in 40-90 grit. I've had to process much of it starting in 220 instead. Sometimes other rock types are the same way. Starting in 220, and it being the only rock (that isn't already pre-processed in rough grit) in a 220 batch, assures that it will not encounter any other non-smoothed rocks and so there will be no rough corners to bang against it or remaining crevices to catch on it. When I saw your photo this morning I was on a small smartphone screen. Now I'm at work and seeing it across a 24" monitor really shows me that it looks just like some pieces I find in southern Oklahoma in an underground buried river gravel bed which produces this material which at times is called the misnomer Boley Agate. The quartz (or whatever it is) matrix material is often not complete and not very solid. And some of the internal breccia is often lousy and porous. I just looked to see if any chance the upper drainage area of the San Jacinto River might access this same formation, and I was shocked to see how short this river is and so far away and it just doesn't seem possible it could be the same formation. So I guess it's just a coincidence that the material looks identical to me.
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Post by HankRocks on Oct 15, 2020 12:55:30 GMT -5
It doesn't hold up well in many cases to the pounding of normal rough grind, in 40-90 grit. I've had to process much of it starting in 220 instead. Sometimes other rock types are the same way. Starting in 220, and it being the only rock (that isn't already pre-processed in rough grit) in a 220 batch, assures that it will not encounter any other non-smoothed rocks and so there will be no rough corners to bang against it or remaining crevices to catch on it. When I saw your photo this morning I was on a small smartphone screen. Now I'm at work and seeing it across a 24" monitor really shows me that it looks just like some pieces I find in southern Oklahoma in an underground buried river gravel bed which produces this material which at times is called the misnomer Boley Agate. The quartz (or whatever it is) matrix material is often not complete and not very solid. And some of the internal breccia is often lousy and porous. I just looked to see if any chance the upper drainage area of the San Jacinto River might access this same formation, and I was shocked to see how short this river is and so far away and it just doesn't seem possible it could be the same formation. So I guess it's just a coincidence that the material looks identical to me. Bob, There is material in the San Jacinto river that by all accounts should not be there, various agates and jaspers that did not originate in SE Texas. In the Geology of Texas book I have, it does show a couple of ancient rivers in past ages that flowed from present day Arkansas and Oklahoma area down to what is now SE Texas. I suspect that any of the Agate/Jasper in the San Jacinto are there because the river has cut through gravel beds deposited by these ancient rivers of the past. Tracing the path of river-tumbled rock from it's origin to it's present location is an interesting area of study. I suspect it can get really complicated as some of these rocks probably end up making 2 or 3 different trips down different rivers at different times. Some of the most prolific agate beds in the county(my opinion) are located along a portion of the Rio Grande in South Texas, a who's who of agate, jasper and wood all washed from many places.
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Post by HankRocks on Oct 15, 2020 13:00:57 GMT -5
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Post by Bob on Oct 15, 2020 13:44:02 GMT -5
Well, I guess it would make sense that any ancient river in Oklahoma as the large Pleistocene sheet retreated would drain toward the Gulf.
I have spent a lot of time outdoors in El Paso, Big Bend, Del Rio, Laredo, etc. but this was all before I got interested in rock tumbling, so I was not looking at what was on the ground, just traversing it or jumping over rattlesnakes and cacti. That is indeed interesting material, and unlike anything I've found elsewhere in the US. I have worked the Rio Grande oh...no further south than Espanola, NM up into southern CO, but have not found much to tumble on it other than interesting granites and quartzites around Del Norte, CO and a bit further W. Yet on the Arkansas Riv in CO, I've found prettier versions of both of those as well as other things too. I have wondered what material might be along the Rio Grande further upstream such as Creede, CO and further W.
Do you know if any interesting rocks wash out of the Chisos Mtns into the Rio Grande? Of course, if the answer is yes they are on land on which collection is forbidden unless in the river bed itself.
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Post by HankRocks on Oct 15, 2020 14:58:26 GMT -5
I have hiked several times in the Chisos Mtns, mainly out of the Basin, South Rim, Emory Peak, etc, etc. Have not see much agate in that area. Most agate occurs in the area outside the Chisos themselves, lots of volcanic activity with corresponding Rhyolite. Needle Peak just on the western tip of the Park is loaded with agate bearing formations. We have walked the river bed on the east side of the park, lots of gravel, not a lot of agate. I personally believe that the famous agate fields to the north of Big Bend Park Woodward, Marfa Bouquet etc. have not managed to wash down to the Rio Grande. I suspect the agate in the lower Rio Grande originated from volcanic deposits long since weathered out from northern Mexico.
The Geologic history of West Texas is a real mixed bag of events. There's a spot at the base of Needle Peak where within 1/4 mile of the truck we could find several types of agate, geodes, petrified wood both in situ and float, Palm Wood, fossil bone(probably ancient mammal) sharks teeth, fossil oyster shells. We also found an old indian knapping site where they used some of the agate as the media. My favorite is a crude palm wood tool. Most of the area is closed off these days.
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Post by Bob on Oct 15, 2020 16:17:03 GMT -5
One year, after coming out of the Chisos early due to a boot problem with a small child, we spent an entire week between the peaks and the river, and along the river, visiting many places especially between Ojinaga and Boquillas, talking to immigrants coming across the river illegally at night and all that. One day I bent down to tie my bootlaces and beside my boot was a brass US Calvary uniform button and a bit of very old black leather. I told this to the park historian and was surprised when she told me that she wished I had collected it rather than left it laying out there. I also was one of the first allowed in as a backpacker into the BB State Park when it opened to the public. Wow. Twice as much wildlife and beauty as the NP. Did a 8 day in there and had the time of my life. I've heard a lot of the beauty if gone due to too much signage, trails, and use, but I don't know if true or not. Want to go into El Solitario badly. Had an 8 day in there planned, but had to abort just before going in when I had a relative in Memphis die and had to head to that place quickly. Will never forget how long it took to cross TX from that corner all the way out the NE corner! Took the better part of 2 days!
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brizzonator
off to a rocking start
Member since July 2020
Posts: 23
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Post by brizzonator on Oct 29, 2020 15:05:27 GMT -5
Thanks all for the thoughtful replies, sorry it took a bit to get back, work has been busy. Thanks all for the analysis of where the San Jacinto material might come from as well, I had noted that in some of the other forum posts when I first started hounding there. For any one interested, I just posted in the photo forum my latest tumble of the material from there, I would love to hear thoughts about it(the material, not my tumbling, which I am still working on, haha).
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brizzonator
off to a rocking start
Member since July 2020
Posts: 23
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Post by brizzonator on Oct 29, 2020 15:14:46 GMT -5
It doesn't hold up well in many cases to the pounding of normal rough grind, in 40-90 grit. I've had to process much of it starting in 220 instead. Sometimes other rock types are the same way. Starting in 220, and it being the only rock (that isn't already pre-processed in rough grit) in a 220 batch, assures that it will not encounter any other non-smoothed rocks and so there will be no rough corners to bang against it or remaining crevices to catch on it. When I saw your photo this morning I was on a small smartphone screen. Now I'm at work and seeing it across a 24" monitor really shows me that it looks just like some pieces I find in southern Oklahoma in an underground buried river gravel bed which produces this material which at times is called the misnomer Boley Agate. The quartz (or whatever it is) matrix material is often not complete and not very solid. And some of the internal breccia is often lousy and porous. I just looked to see if any chance the upper drainage area of the San Jacinto River might access this same formation, and I was shocked to see how short this river is and so far away and it just doesn't seem possible it could be the same formation. So I guess it's just a coincidence that the material looks identical to me. Bob, There is material in the San Jacinto river that by all accounts should not be there, various agates and jaspers that did not originate in SE Texas. In the Geology of Texas book I have, it does show a couple of ancient rivers in past ages that flowed from present day Arkansas and Oklahoma area down to what is now SE Texas. I suspect that any of the Agate/Jasper in the San Jacinto are there because the river has cut through gravel beds deposited by these ancient rivers of the past. Tracing the path of river-tumbled rock from it's origin to it's present location is an interesting area of study. I suspect it can get really complicated as some of these rocks probably end up making 2 or 3 different trips down different rivers at different times. Some of the most prolific agate beds in the county(my opinion) are located along a portion of the Rio Grande in South Texas, a who's who of agate, jasper and wood all washed from many places. Thanks, I was wondering about that and I know it's been bandied about before in response to the other posts, including the one you link who looks to have acquired some real prizes there. I can tell you that near the place I gather there is a section where the river is eroding out stones already embedded in the soil, but not sure if that is from long ago or just from one of the massive floods it has had in the past(I suspect the latter). I posted below that I just posted pics from a tumble of some of my material there). There is some stuff that appears again and again(for instance we have a lot of palmwood in this section of Texas, but the unusual stuff looks about as alike as a shotgun blast, though I've only been hounding it a few months (my "get myself out of the house CV19" hobby that I've been loving).
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Post by HankRocks on Oct 29, 2020 16:21:59 GMT -5
Bob, There is material in the San Jacinto river that by all accounts should not be there, various agates and jaspers that did not originate in SE Texas. In the Geology of Texas book I have, it does show a couple of ancient rivers in past ages that flowed from present day Arkansas and Oklahoma area down to what is now SE Texas. I suspect that any of the Agate/Jasper in the San Jacinto are there because the river has cut through gravel beds deposited by these ancient rivers of the past. Tracing the path of river-tumbled rock from it's origin to it's present location is an interesting area of study. I suspect it can get really complicated as some of these rocks probably end up making 2 or 3 different trips down different rivers at different times. Some of the most prolific agate beds in the county(my opinion) are located along a portion of the Rio Grande in South Texas, a who's who of agate, jasper and wood all washed from many places. Thanks, I was wondering about that and I know it's been bandied about before in response to the other posts, including the one you link who looks to have acquired some real prizes there. I can tell you that near the place I gather there is a section where the river is eroding out stones already embedded in the soil, but not sure if that is from long ago or just from one of the massive floods it has had in the past(I suspect the latter). I posted below that I just posted pics from a tumble of some of my material there). There is some stuff that appears again and again(for instance we have a lot of palmwood in this section of Texas, but the unusual stuff looks about as alike as a shotgun blast, though I've only been hounding it a few months (my "get myself out of the house CV19" hobby that I've been loving). I need to get up to the river and do some collecting, weather is getting nice for that.
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kyoti
has rocks in the head
Member since June 2020
Posts: 542
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Post by kyoti on Nov 1, 2020 8:17:56 GMT -5
If you don't want to change the shape of the rock, you can start with the 220 grit to help smooth just the rock surface. If you see any surface pits or little crevices, bear in mind they will trap grit that you will have to work at removing. The polish phase will really show any cracks or pits as white spots or lines. Using a hose spray nozzle will remove most of it if you clean it before the rock dries.
If the rock turns out to be soft like the Travertine we have in Dallas, it will round and smooth nicely in the 220.
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