Post by Bob on Aug 17, 2020 11:35:12 GMT -5
Because tumbling large rocks seems to be a thing here now, and it's been a large part of my tumbling for about 5 years, possibly I have something to contribute to help others. So instead of writing some treatise, I'm going to post now and then some threads with this name but change the numbers at end so they don't get mixed up. There are quite a few technical tips for me to mention, but posting those will take time and can be done now and then.
The largest rock I have tumbled so far is has only 1/2" clearance flat to flat in my 40lb Lortone steel barrel! It looks like a small football.
What is a monster rock? I suppose for me, it's one that is grapefruit size or larger. I just held my hands together in a circle and measured that hole. It was 5" trying to mimic a grapefruit. So I guess once a dimension gets to 5" it seems to me there are certain challenges.
Some have taken 3 years. Removing say 1mm from a rock the size of a quarter vs doing it from the entire surface of a monster rock might at first seem like the same project. If it takes a month, well, the size of the rock doesn't matter. I used to think that too until I tried it on large rocks. It doesn't work that way. It can take the better part of a year to remove 1mm from a tough Brazilian agate I've learned if it's quite large and one has no barrel larger than the diameter of the 40lber. So tumbling these monsters takes a dang lot of patience.
I no longer take my largest polished Brazilian agate to rock shops for fun any more. Strange things happen. They always want to buy it. They just keep holding it and saying something like this "You know, I sell polished rocks. I don't buy them for myself. But I've been in business 30 years and have never had a customer come in with a huge polished rock like this. Didn't know anyone was doing these. I want this. How much?" It wasn't for sale. But the offers just keep going up and up. So I have wondered if when I retire someday I might be able to translate my experience and supply of polished large rocks into making some money to help pay for this hobby. On eBay it seems that listing for "large polished rocks" mean anything larger than 1 quarter!
The trouble with that plan is once you work on a single rock for 2-3 years, you don't want to sell it unless it's for a decent chunk of change. Even then, are you making a profit given the time and grit you spent on the thing? I've developed a single rock tracking sheet in an attempt to measure this which I'm totally willing to share if this image upload ever works for me.
I have about 4,000 lbs of rock in inventory just for my personal hobby. Unfortunately--because I need to relocate next year due to my recent remarriage. Many of those rocks are what you would probably call monsters, but just enough to get inside the flat-to-flat distance of my 40lb barrel with enough clearance to tumble. So at times, I have to measure the rocks in the field before I collect them.
Because backpacking has been a big part of my life, and carrying weight on my back is easy for me, transporting a load of large cobbles is something done quite a bit. For instance, I've carried back large rocks to tumble from 300' high glacial moraines in Ontario and been so hunched over getting back to my vehicle that had someone seen me they probably would have thought I was going to disable myself. But could they have seen my face, I was so excited and happy to think about the years of tumbling fun these rocks would be!
Well, time to end but with one technical tip. There are parts of posts that wonder about tumbling one large rock with other good rocks and whether the large rock will damage the smaller good rocks. Let's say for instance I have one large rock in a barrel that is 2/3 or more of the diameter of the barrel, and the rest are typical this and that to be tumbled--not just filler rocks but good rocks to be kept when done. It seems there are concerns at times that the large rock will destroy the smaller rocks.
This doesn't happen for me UNLESS the large rock and most of the other rocks still have hard corners that can "catch" against each other in the interior cascade fall face in the tumbler. So, if I was putting a large rock from the field in a tumbler today, I would not also put in rough stuff with it if that rough stuff was valuable to me. Rather, that other stuff needs to be ground done in rough (usually only 1 week is enough) so at least no sharp corners left. My theory is that the rounding of the edges helps prevent that monster from crushing some of the others when they catch and instead everything slips by instead of catching. Sometimes though I put in other cornered rough anyway knowing any fractures I can't see will be taken care of by the monster and the ultimate processed quality will be improved.
If the monster rock has some very rough edges and is more than 2/3 to 3/4 of the barrel diameter, I will often tumble it with only quartz river gravel (1/2 or so) until the rough edges are gone before I put other valuable rocks in there. This is true the more that monster has a specific gravity heavier than average. I'm currently working quite a few pieces of large psilomelane and these will badly beat up other rocks if the p is much larger than them and the p isn't yet rounded.
Last week, I got my largest piece of Mary Ellen Jasper ever, it's about 5x3x2" and virtually rectangular in shape with 90 degree corners. When I lifted this thing I could tell this material is heavier than most rocks--possible solely because of its hematite content. So it's being begun with those quartz stream stones instead of my other good rocks in a 20lb barrel.
Whenever I travel and stop at rock shops, I ask them if anyone else in USA is frequently tumbling rocks larger than orange size like me. The answer has always been no are you crazy, but once it was yes. If memory serves, that person was in Oregon. Can't recall at the moment if I reached out or not. It's so fun to see this subject being of interest now. Be prepared to eat through a lot of rough grit!
The largest rock I have tumbled so far is has only 1/2" clearance flat to flat in my 40lb Lortone steel barrel! It looks like a small football.
What is a monster rock? I suppose for me, it's one that is grapefruit size or larger. I just held my hands together in a circle and measured that hole. It was 5" trying to mimic a grapefruit. So I guess once a dimension gets to 5" it seems to me there are certain challenges.
Some have taken 3 years. Removing say 1mm from a rock the size of a quarter vs doing it from the entire surface of a monster rock might at first seem like the same project. If it takes a month, well, the size of the rock doesn't matter. I used to think that too until I tried it on large rocks. It doesn't work that way. It can take the better part of a year to remove 1mm from a tough Brazilian agate I've learned if it's quite large and one has no barrel larger than the diameter of the 40lber. So tumbling these monsters takes a dang lot of patience.
I no longer take my largest polished Brazilian agate to rock shops for fun any more. Strange things happen. They always want to buy it. They just keep holding it and saying something like this "You know, I sell polished rocks. I don't buy them for myself. But I've been in business 30 years and have never had a customer come in with a huge polished rock like this. Didn't know anyone was doing these. I want this. How much?" It wasn't for sale. But the offers just keep going up and up. So I have wondered if when I retire someday I might be able to translate my experience and supply of polished large rocks into making some money to help pay for this hobby. On eBay it seems that listing for "large polished rocks" mean anything larger than 1 quarter!
The trouble with that plan is once you work on a single rock for 2-3 years, you don't want to sell it unless it's for a decent chunk of change. Even then, are you making a profit given the time and grit you spent on the thing? I've developed a single rock tracking sheet in an attempt to measure this which I'm totally willing to share if this image upload ever works for me.
I have about 4,000 lbs of rock in inventory just for my personal hobby. Unfortunately--because I need to relocate next year due to my recent remarriage. Many of those rocks are what you would probably call monsters, but just enough to get inside the flat-to-flat distance of my 40lb barrel with enough clearance to tumble. So at times, I have to measure the rocks in the field before I collect them.
Because backpacking has been a big part of my life, and carrying weight on my back is easy for me, transporting a load of large cobbles is something done quite a bit. For instance, I've carried back large rocks to tumble from 300' high glacial moraines in Ontario and been so hunched over getting back to my vehicle that had someone seen me they probably would have thought I was going to disable myself. But could they have seen my face, I was so excited and happy to think about the years of tumbling fun these rocks would be!
Well, time to end but with one technical tip. There are parts of posts that wonder about tumbling one large rock with other good rocks and whether the large rock will damage the smaller good rocks. Let's say for instance I have one large rock in a barrel that is 2/3 or more of the diameter of the barrel, and the rest are typical this and that to be tumbled--not just filler rocks but good rocks to be kept when done. It seems there are concerns at times that the large rock will destroy the smaller rocks.
This doesn't happen for me UNLESS the large rock and most of the other rocks still have hard corners that can "catch" against each other in the interior cascade fall face in the tumbler. So, if I was putting a large rock from the field in a tumbler today, I would not also put in rough stuff with it if that rough stuff was valuable to me. Rather, that other stuff needs to be ground done in rough (usually only 1 week is enough) so at least no sharp corners left. My theory is that the rounding of the edges helps prevent that monster from crushing some of the others when they catch and instead everything slips by instead of catching. Sometimes though I put in other cornered rough anyway knowing any fractures I can't see will be taken care of by the monster and the ultimate processed quality will be improved.
If the monster rock has some very rough edges and is more than 2/3 to 3/4 of the barrel diameter, I will often tumble it with only quartz river gravel (1/2 or so) until the rough edges are gone before I put other valuable rocks in there. This is true the more that monster has a specific gravity heavier than average. I'm currently working quite a few pieces of large psilomelane and these will badly beat up other rocks if the p is much larger than them and the p isn't yet rounded.
Last week, I got my largest piece of Mary Ellen Jasper ever, it's about 5x3x2" and virtually rectangular in shape with 90 degree corners. When I lifted this thing I could tell this material is heavier than most rocks--possible solely because of its hematite content. So it's being begun with those quartz stream stones instead of my other good rocks in a 20lb barrel.
Whenever I travel and stop at rock shops, I ask them if anyone else in USA is frequently tumbling rocks larger than orange size like me. The answer has always been no are you crazy, but once it was yes. If memory serves, that person was in Oregon. Can't recall at the moment if I reached out or not. It's so fun to see this subject being of interest now. Be prepared to eat through a lot of rough grit!