tkvancil
fully equipped rock polisher
Member since September 2011
Posts: 1,546
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Post by tkvancil on Jan 27, 2016 11:51:26 GMT -5
I know that many agates are prone to fractures. Montanas and Lakers come to mind right away. I will send a fractured agate through to polish if the fracture is "tight" and doesn't hold slurry. Fractures that run close to perpendicular to the rocks surface are least problematic. Those that run closer to parallel however often chip on the edge of the fracture line. In my experience at least.
My concern is that my tumbling MIGHT be causing some fractures. Although an absence of chips, spalls or frosting says my formula is right. Currently running some Lakers and many are fractured to one degree or another. I just looked at some of the rough not yet in the tumblers and can see the fractures.
Hence the question ... Other than inspecting each rock before tumbling and somehow keeping track of them ... Is there a reliable way to tell when the fractures occurred?
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Post by pauls on Jan 27, 2016 16:18:09 GMT -5
I tumble heaps of Australian Agate Creek Agates and they are exactly the same, I think they are born with fractures.
I put the small nodules in whole to remove the surface crust then saw them along any large cracks that appear, any surface fractures I try to grind out. Once I have removed the pre-existing cracks no more appear, though sometimes cracks are deeper than I thought and need a second touch up. I always start with largish pieces, that way if they need grinding or sawing to remove fractures there's room to do that and still have decent size finished rocks, the small pieces I saw off go back in to round off a bit then go into the seconds pile, I do a seperate batch of seconds when I have enough, kids still like them.. Some just are never going to be any good these I just put in the seconds pile.
I never hit Agates with a hammer, that causes fractures for sure and too much waste of lovely material, larger pieces say Apricot size I take a saw cut off centre so I can get a slab if its good, then I might saw the half pieces in half again. Really large pieces I allow plenty of room for cabbing thickness slabs, but if the material is nothing fancy I cut it into chunky pieces.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,169
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Post by jamesp on Jan 28, 2016 9:19:44 GMT -5
After the second or 3rd week a clean out and rejection of misfits. Usually 3 weeks, fractures more visible about 3 weeks.
Many can be tile sawed opposite fracture and hammer finished, put back in tumbler.
Darn fractures.
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Fossilman
Cave Dweller
Member since January 2009
Posts: 20,685
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Post by Fossilman on Jan 28, 2016 10:17:51 GMT -5
Montana's,I don't worry about fractures, they are mostly all healed...Other agates with fractures, I cut the fractured area out and discard it into the rock garden, throw it into the tumbler.... Some fractures are just part of the game and just roll with it.........
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tkvancil
fully equipped rock polisher
Member since September 2011
Posts: 1,546
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Post by tkvancil on Jan 28, 2016 13:33:01 GMT -5
pauls jamesp and fossilman I deal with the fractures in the same way you guys do. For the most part consider it part of the game. Hammering not the best however a punch or chisel and a light touch does okay. When buying crushed agate there is always a lot of fractures. Can't tell if they were there all along or if the crushing caused it. Crushing probably has to make more.
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Post by Drummond Island Rocks on Jan 28, 2016 14:10:22 GMT -5
Hammer and machine broken agates can be challenging but that don't stop me from swinging a big hammer at them. Sometimes it is just a time management deal. Buckets start filling with end cuts and the tumblers need food. I have never broken a rock with a chisel. They all get hit starting with a 14 pound sledge then fine refinements with a 3 pounder. Best example I have for making lemonade out of lemons was the mechanically crushed Brazilian agates that were sent out for the 2014 contest. Scroll to the bottom for the fractured rough then scroll up for the finished pieces. forum.rocktumblinghobby.com/thread/66971/good-pic-heavyChuck
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jamesp
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Member since October 2012
Posts: 36,169
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Post by jamesp on Jan 28, 2016 15:02:27 GMT -5
Yes, those were beat up pretty good Chuck.
Mentioned this before, rock shop in north Atlanta had a rock crusher for making tumbles. It made terrible tumbles.
It does boil down to time management. Or a lot of material to destroy to get good pieces.
My best tumbles come from 1 to 2 inch thick slabs. yep, I saw a big nodule into 1 - 2 inch slabs and use a small 4 ounce hammer to strike tumbles off the flat faces of the slab. The weight of the slab and the flat impact surface way improves control and fractures. Whether buying or self collecting I ask for big sawable nodules to slab thick.
I flip the slab back and forth striking the side with the overhang under the sawn surface to be struck. Flat hammer face ground to radius about like a tennis ball or soft ball.
Small pieces are much harder to reduce, as are odd shapes.
And yes, I have an 18 inch saw which makes the slab thing work.
And it darn sure depends on the type of rock.
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Post by Drummond Island Rocks on Jan 28, 2016 15:18:22 GMT -5
Yes, those were beat up pretty good Chuck. Mentioned this before, rock shop in north Atlanta had a rock crusher for making tumbles. It made terrible tumbles. It does boil down to time management. Or a lot of material to destroy to get good pieces. My best tumbles come from 1 to 2 inch thick slabs. yep, I saw a big nodule into 1 - 2 inch slabs and use a small 4 ounce hammer to strike tumbles off the flat faces of the slab. The weight of the slab and the flat impact surface way improves control and fractures. Whether buying or self collecting I ask for big sawable nodules to slab thick. I flip the slab back and forth striking the side with the overhang under the sawn surface to be struck. Flat hammer face ground to radius about like a tennis ball or soft ball. Small pieces are much harder to reduce, as are odd shapes. And yes, I have an 18 inch saw which makes the slab thing work. And it darn sure depends on the type of rock. As bad as that rough was I did not throw away one piece. Every piece was tumbled several weeks then inspected. I then ground on every single piece with an 80 grit diamond wheel till they were free of defects. This can be done when working on a small scale of 3 pounds. Those of you working on larger scales would not find grinding every rock very efficient. I grind flaws out of my tumbles every week. Its just part of my process. All of the rocks I grind this Saturday are the ones that I will pull from stage one next Saturday. This is how I guarantee to have batch of tumbles done every week. Chuck
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Post by pauls on Jan 28, 2016 15:50:35 GMT -5
I do the same as Chuck, though I use a 9 Kilogram (20pound) gas cylinder as a barrell. Hard to say the weight of stones though I can barely lift it, probably more than a cubic foot of stones say 50-60 pound, Each day I check it and grab a few handful of rocks out, this gives me an idea about how the grit is going, sort through and grind a few, saw a few cracks out, toss a few and put seconds aside for a seperate batch, recent additions that need more time just go straight back, then I top up with some new pieces. It doesn't take long.
After about a week or so I usually have enough really good stones to feed the vibe, it takes a bit longer to get a batch of seconds because I dont give up on very many.
Paul
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,169
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Post by jamesp on Jan 28, 2016 16:32:06 GMT -5
The best way to get good tumbles is doing that grind maintenance like weekly like you guys are doing.
Hands down. Why tumble 100% of the rock if only 10% has an offending bump or divot, which is often the case. A little of that goes a long way to AAA grade tumbles.
grading tumbles like diamonds....
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Fossilman
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Member since January 2009
Posts: 20,685
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Post by Fossilman on Jan 29, 2016 13:00:37 GMT -5
I grind most of my tumbles anymore,unless its river rock(it's been helped along a bit,already)...
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