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Post by Deleted on Oct 9, 2014 14:48:34 GMT -5
Thanks for the kind words Daniel. With the advent of cheap industrial diamonds, oxides had competition. Flowing forward from your thought above. I wonder how much loose diamond we need and how long it would last. It may end up being cheaper than silicon carbide due to longevity www.ebay.com/itm/Synthetic-Diamond-Powder-50-60-Mesh-50Grit-weight-100-cts-20-Gram-/271625613916?pt=LH_DefaultDomain_0&hash=item3f3e25f25cRetail at $1.40 a gram. Available online for $100 # in myriad grit sizes. Imagine, spin in the rough grind long enough until ready, pour out barrel, sieve out your subject stones catching all the liquid in a bucket, pour out all the slurry, rinse your diamonds and start another batch. Need to get a few ounces to Chuck or Jim to check in their rough tumbles. Cubic Boron Nitride almost as hard as diamond, might be worth trying too.
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Post by deb193redux on Oct 9, 2014 16:21:53 GMT -5
longevity of the diamond, and longevity of our ability to use it are two different things. once fine particles get embedded in thick mud, it is easier to toss it and begin fresh. I guess diamond could be separated form mud in some sort of water column apparatus, but ...
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akroes
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Post by akroes on Oct 9, 2014 18:55:18 GMT -5
Do you take it out and play with it occasionally? It is good to keep your mind active and well exercised.
Where are you going camping? Are there rocks there to collect? Jean Too funny - I had to read that a second time to see that you weren't making a non-family-friendly joke! Camping in NE Wisconsin - granite everywhere, and not much else where I'll be. I do know a spot where there are some quartz crystals, but they are extremely small (1/4") and the area is *very* well picked over. I'll keep an eye out though, and maybe I can take a side trip a bit further north to catch some Lake Superior beach rocks/agate. Tony
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Post by rockpickerforever on Oct 9, 2014 19:15:56 GMT -5
Glad you took it in fun as intended. Granite, huh? Sometimes granite can be fun. Gathering agates in Lake Superior could be productive.
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Post by Deleted on Oct 9, 2014 20:49:46 GMT -5
jamesp - 'abrasives' is the category of materials used to alter the surface of something - Grit, pre-polish, and polish are the names given to the abrasives used in these steps. Hey everyone!! I have been contemplating this thread deeply. In fact, I spent an hour with a commercial lapidary today. He polishes 16-18" rounds of pet wood for commercial sales. Dude knows a bit. Jamesp did a thread in which we can visually see this the progressions of the surface of obsidians. Jim was very thorough and carefully illustrated each step pretty well. ANYONE can see the changes. I will change the term I used before, "scratches". I will now use the term used by the commercial metal polishing house I spoke with. The metal surface prep/polishers call the texture of the surface a "profile". The surface of a stone doesn't necessarily have scratches but it does indeed have a "profile". Looking at Jim's obsidian images you can SEE the surface profile change from large grits to polish. There is no reason to believe that when we get to "polish" that the surface profile is changing any differently than it did when we progressed from 220 to 500 mesh abrasives. It is simply doing so in such a small fashion as to stop disturbing the reflection of lightwaves.
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jamesp
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Post by jamesp on Oct 9, 2014 22:14:50 GMT -5
jamesp - 'abrasives' is the category of materials used to alter the surface of something - Grit, pre-polish, and polish are the names given to the abrasives used in these steps. Hey everyone!! I have been contemplating this thread deeply. In fact, I spent an hour with a commercial lapidary today. He polishes 16-18" rounds of pet wood for commercial sales. Dude knows a bit. Jamesp did a thread in which we can visually see this the progressions of the surface of obsidians. Jim was very thorough and carefully illustrated each step pretty well. ANYONE can see the changes. I will change the term I used before, "scratches". I will now use the term used by the commercial metal polishing house I spoke with. The metal surface prep/polishers call the texture of the surface a "profile". The surface of a stone doesn't necessarily have scratches but it does indeed have a "profile". Looking at Jim's obsidian images you can SEE the surface profile change from large grits to polish. There is no reason to believe that when we get to "polish" that the surface profile is changing any differently than it did when we progressed from 220 to 500 mesh abrasives. It is simply doing so in such a small fashion as to stop disturbing the reflection of lightwaves. I never could figure out why the profile always looked sand blasted and hardly any scratches. Every step. Just like acid etched glass. That my friend is a mystery. And profile is the way to describe it. Why pits, and few linear scratches. Please tell. Scratched profile from an abrasive rotary wheel. Abrasive held in place by matrix or sintering, sliding and darn sure scratching But pits or frosting profile when rotary tumbling ?? Pits from a vib, yes, makes sense, vibratory impingement, rocks bouncing off of each other. I thought a rotary abrades with a sliding action, a linear motion. Grit must be rolling between the rocks? Causing the pits? ell if I know
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Post by deb193redux on Oct 10, 2014 7:30:21 GMT -5
pitts are unlikely to come from grit. you can have voids in the stone that get revealed, or even softer pockets in the stone, that get revealed and then form a pit under abrasion, or you can have a crystal structure and composition that have pitt-shaped pieces break out when rocks bump rocks.
but one rock coated in grit/slurry, sliding over another rock coated in grit is going to abrade the surface into the new profile (by making many many un-oriented scratches) - not produce pitt. those will need to come from tbe collision of rock or the composition of the rock or both.
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jamesp
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Post by jamesp on Oct 10, 2014 8:12:24 GMT -5
pitts are unlikely to come from grit. you can have voids in the stone that get revealed, or even softer pockets in the stone, that get revealed and then form a pit under abrasion, or you can have a crystal structure and composition that have pitt-shaped pieces break out when rocks bump rocks. but one rock coated in grit/slurry, sliding over another rock coated in grit is going to abrade the surface into the new profile (by making many many un-oriented scratches) - not produce pitt. those will need to come from tbe collision of rock or the composition of the rock or both. I like what you say. Makes perfect sense. Maybe pits is a bad description on my part. It puzzles me that the profile is so frosted and not linearly scratched in these photos of obsidian and glass in a rotary tumbler turning a very slow 12 RPM, 7/8 full barrel and thick sugar slurry. Basically a zero impact situation. Glass, 30 grit, about as homogenous as a material can get. This is why the word pits was used. Weird wear profile for a rotary tumbler. Obsidian after a 220 finish, no scratches, just a frosted look Obsidian after a 400 finish, same thing, frost And just to do a test, skipped 1000 and went to 1 micron polish to smooth the 400 finish, accentuating the 400 finish So I am mystified by the fact there is no linear scratches, but an incredible sand blasted profile.
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Post by deb193redux on Oct 10, 2014 10:20:12 GMT -5
I do think it makes sense to approach frosting differently - but I am not sure I have particular frosting answers. Your pictures surely show something that is not strictly a pattern of scratches. So where do the patterns come from if not form the direct abrasion of grit? It has to come from mechanical processes, or perhaps physical such as heat/friction/soaking, or even chemical reactions of components of the rock on the surface.
I have read discussions of surface crazing, and seen examples. I am not sure I fully understand its origins. Likely the mechanical contact of rocks on the load, but also the properties of the material (perhaps crystal habits or planes of weakness in the habit, or even in the case of obsidian, the fact that the material is amorphous solid (non-crystalline) material) allow the emergence of a surface layer that will react and display different from the underlying stone. It is also possible that surface layers come about from friction/heat, or from the micro-penetration of water into the micro pore space of the stone.
To me, the last picture of mahogany obsidian, it looks like there is a distinct surface layer that is coming apart. I suspect this is mechanical action because glass is described as more brittle than silicate minerals with crystal structure. Just my theory, but I think most grit slurries are thicker and of course the suspended grit is relatively large compared to often thinner polish slurries with vastly smaller particles suspended. In this context, two stones touching in grit are touching at many points of grit-contact (like many marbles pressed between your two palms) and the same two stones touching in polish would be more like your two palms pressed together with some pepper, or even toner, between them. The former is more like many jabs, the latter is much more like a slap.
I think a key point is that in trying to speak about a finer scratch theory of polishes, we have to distinguish between frosting/crazing that always occurs, and that which typically occurs on just some materials. The crystal structure and the fineness of the grain, and the nature of the impurities, and the variations of hardness within material would all have to be considered.
I think a good lapidary has a store of practical knowledge about what will work to polish various difficult materials, as well as a sense of when to try something else. This high-level real-world ability may not explicitly require full understanding of the underlying mechanics and physical chemistry. I know I don't understand it all, even if I can make a list of factors involved.
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jamesp
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Post by jamesp on Oct 10, 2014 10:42:54 GMT -5
I do think it makes sense to approach frosting differently - but I am not sure I have particular frosting answers. Your pictures surely show something that is not strictly a pattern of scratches. So where do the patterns come from if not form the direct abrasion of grit? It has to come from mechanical processes, or perhaps physical such as heat/friction/soaking, or even chemical reactions of components of the rock on the surface. I have read discussions of surface crazing, and seen examples. I am not sure I fully understand its origins. Likely the mechanical contact of rocks on the load, but also the properties of the material (perhaps crystal habits or planes of weakness in the habit, or even in the case of obsidian, the fact that the material is amorphous solid (non-crystalline) material) allow the emergence of a surface layer that will react and display different from the underlying stone. It is also possible that surface layers come about from friction/heat, or from the micro-penetration of water into the micro pore space of the stone. To me, the last picture of mahogany obsidian, it looks like there is a distinct surface layer that is coming apart. I suspect this is mechanical action because glass is described as more brittle than silicate minerals with crystal structure. Just my theory, but I think most grit slurries are thicker and of course the suspended grit is relatively large compared to often thinner polish slurries with vastly smaller particles suspended. In this context, two stones touching in grit are touching at many points of grit-contact (like many marbles pressed between your two palms) and the same two stones touching in polish would be more like your two palms pressed together with some pepper, or even toner, between them. The former is more like many jabs, the latter is much more like a slap. I think a key point is that in trying to speak about a finer scratch theory of polishes, we have to distinguish between frosting/crazing that always occurs, and that which typically occurs on just some materials. The crystal structure and the fineness of the grain, and the nature of the impurities, and the variations of hardness within material would all have to be considered. I think a good lapidary has a store of practical knowledge about what will work to polish various difficult materials, as well as a sense of when to try something else. This high-level real-world ability may not explicitly require full understanding of the underlying mechanics and physical chemistry. I know I don't understand it all, even if I can make a list of factors involved. Thanks for your time Daniel. I certainly do not understand what is going on. The black obsidian lends good photographic results. I feel certain that the silicate materials are doing the same thing. I will try the same photos on dark silicates to see they have frost type wear that shows up in the photos. I am suspicious that they are judging from the sparkles visible in the glare when inspecting the progress of the 30, 220 and 500. Never have taken macros of the silicates, they are sure not a problem as obsidian is. It all seems strange for a rotary tumbler to have the frost type abrasion.
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Deleted
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Post by Deleted on Oct 10, 2014 11:01:15 GMT -5
jamesp - When you have brazilians of abrasive particles rubbing on the stones, none of them will be in the same line. The "scratches" will be random, overlapping each other at random angles and continuously throughout the surface of the stone. Randomized enough, such as in a tumbler or my case a sphere machine, and all you see is what you show us in your images. That is my story and I am sticking with it!
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Post by rockpickerforever on Oct 10, 2014 11:28:21 GMT -5
Apparently I have the mind of a 9-year old girl! (I keep it in a jar on my desk!) Tony Tony, you know I'm just funning you about this, but perhaps I should explain... Do you take it out and play with it occasionally? It is good to keep your mind active and well exercised.
Where are you going camping? Are there rocks there to collect? Jean Too funny - I had to read that a second time to see that you weren't making a non-family-friendly joke! Camping in NE Wisconsin - granite everywhere, and not much else where I'll be. I do know a spot where there are some quartz crystals, but they are extremely small (1/4") and the area is *very* well picked over. I'll keep an eye out though, and maybe I can take a side trip a bit further north to catch some Lake Superior beach rocks/agate. Tony It's something my husband likes to say about some people he knows: "If he had a brain, he'd take it out and play with it!"
So by you saying that you keep your brain in a jar on the desk, just opened you up for that. Love it when people can poke fun at themselves, and we're all here to help! Jean
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Post by mohs on Oct 10, 2014 12:13:14 GMT -5
Interesting discussion ! I certainly have random scratches but I think that because my grinding not very precise mostly
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jamesp
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Post by jamesp on Oct 10, 2014 12:15:33 GMT -5
jamesp - When you have brazilians of abrasive particles rubbing on the stones, none of them will be in the same line. The "scratches" will be random, overlapping each other at random angles and continuously throughout the surface of the stone. Randomized enough, such as in a tumbler or my case a sphere machine, and all you see is what you show us in your images. That is my story and I am sticking with it! Check out this piece of broken glass. The top surface was polished. Looks like a gun target to me after 30 grit got a hold of it. I agree with you about the mechanics. I agree with all that was said. I just do not understand the profile in the photo. Or the other frosting wear on the other grits.
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Post by Deleted on Oct 10, 2014 12:18:46 GMT -5
Apparently I have the mind of a 9-year old girl! (I keep it in a jar on my desk!) Tony Tony, you know I'm just funning you about this, but perhaps I should explain... I was thinking the brain in the jar was that of a 9 year old girl, a specimen he keeps in a jar.
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Post by Deleted on Oct 10, 2014 12:20:27 GMT -5
jamesp - When you have brazilians of abrasive particles rubbing on the stones, none of them will be in the same line. The "scratches" will be random, overlapping each other at random angles and continuously throughout the surface of the stone. Randomized enough, such as in a tumbler or my case a sphere machine, and all you see is what you show us in your images. That is my story and I am sticking with it! Check out this piece of broken glass. The top surface was polished. Looks like a gun target to me after 30 grit got a hold of it. I agree with you about the mechanics. I agree with all that was said. I just do not understand the profile in the photo. Or the other frosting wear on the other grits. so then, the grit starts to cut the stone and cleaves before making a long scratch? Each cut made by the grit is more like a nip?
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Post by mohs on Oct 10, 2014 12:25:33 GMT -5
hhhmmm... I like what was said about undercutting rocks matrix are not uniform lots of different micro bits
but then james bring in glass which should be a fairly uniform material yet under intense magnification we can see how electrons jump to different shell levels perhaps...
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jamesp
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Post by jamesp on Oct 10, 2014 12:28:07 GMT -5
Check out this piece of broken glass. The top surface was polished. Looks like a gun target to me after 30 grit got a hold of it. I agree with you about the mechanics. I agree with all that was said. I just do not understand the profile in the photo. Or the other frosting wear on the other grits. so then, the grit starts to cut the stone and cleaves before making a long scratch? Each cut made by the grit is more like a nip? I am still looking for the sand blaster that put such deep divots in that piece of glass. They don't seem deep to you ? That photo represents 1 inch left to right. So about 4X magnification. those are some deep holes !!??
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Post by mohs on Oct 10, 2014 12:30:00 GMT -5
a sand blaster at this fine of tumbled smoothing is probably a good analogy
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jamesp
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Post by jamesp on Oct 10, 2014 12:41:44 GMT -5
a sand blaster at this fine of tumbled smoothing is probably a good analogy Still puzzled by the deep divots that the 30 grit caused in the photo above Ed.
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