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Post by Jugglerguy on Aug 5, 2016 22:15:46 GMT -5
On my recent trip to the Keweenaw Peninsula, I visited a mine tailings pile of a conglomerate rock. Most of the rock looked like this, but much of had a thin layer of what I think is chrysocolla along just the face of the rock. This is a big rock, the aggregate in it is really large. We were able to find one decent sized rock and a couple smaller ones with the chrysocolla going all through the rock (instead of just a thin layer where it broke) and also much smaller aggregate. Here is a cut face of the rock above. Here's a cab I made of it tonight. It doesn't really show up in the photo, but the chrysocolla is undercutting. I thought it might, but I don't know how to avoid it. Does anyone have any tips for me to avoid the undercutting?
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barclay
has rocks in the head
Lowly Padawan of rocks
Member since November 2011
Posts: 510
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Post by barclay on Aug 5, 2016 22:33:38 GMT -5
If memory serves chrysocolla is an evaporate (crystals dry out from water) so the structure and the chemistry make it soft. The trick i believe is to use gentle but firm pressure on the wheels. By firm i mean hold the dop stick so the stone does not wiggle where it touches the wheel. If you push too hard, especially on a soft wheel, the surface of the wheel deforms a bit and preferentially digs out the softer material. You may want to try stabilizing with a CA type glue to solidify the chrysocolla a bit.
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Post by vegasjames on Aug 6, 2016 1:03:33 GMT -5
If memory serves chrysocolla is an evaporate (crystals dry out from water) so the structure and the chemistry make it soft. The trick i believe is to use gentle but firm pressure on the wheels. By firm i mean hold the dop stick so the stone does not wiggle where it touches the wheel. If you push too hard, especially on a soft wheel, the surface of the wheel deforms a bit and preferentially digs out the softer material. You may want to try stabilizing with a CA type glue to solidify the chrysocolla a bit. Technically chrysocolla is a copper silicate, but the name is also applied to a variety of unidentified copper ores. In this stone it appears some of the copper ores include malachite, azurite and posibly rosasite.
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Post by mohs on Aug 6, 2016 10:18:36 GMT -5
cool rock & cabbing !
would it be beneficial to try hand lapping it now that its domed? the matrix and the chys are probably fairly soft going to a hand lap operation you might be able to control the undercutting better...
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Tommy
Administrator
Member since January 2013
Posts: 12,884
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Post by Tommy on Aug 6, 2016 12:44:50 GMT -5
Here's a cab I made of it tonight. It doesn't really show up in the photo, but the chrysocolla is undercutting. I thought it might, but I don't know how to avoid it. Does anyone have any tips for me to avoid the undercutting? There is really no way to completely avoid it - the severity of it will be directly related to the hardness of the copper mineral in relation to the host matrix. There are some tricks you can use to minimize it. For me, the number one thing is to focus on the wheel that is still removing BOTH surfaces equally and go as far as you possibly can on this wheel. For instance with your material I would spend a LOT of time on my 220 hard wheel making sure the dome was perfect (side to side and front to back) which means every high spot and valley is gone and flat spots are minimal. When it's perfect I would move on to give it a quick hit on the 140 soft just to remove any remaining flat spots - don't spend too much time here because your girdle will dive thin and cause you to spend time and material reshaping things. After this I skip as many wheels as I can until I'm on a wheel that will barely remove any material (if any) from either surface. My wheels sequence on a stone like this might be 100, 220(hard), 140, 3000 briefly, 14k, poish (either 50k wheel or AO depending how porous the stone is). I might even skip the 3000 all together. The more wheels you skip the longer you have to spend after the skip. I'll spend a good long time on the 14k unless the undercutting is still occurring - if it is still occurring heavily at 14k then there's not a whole lot you can do about it other than stablizing it before you start. Hope this helps.
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Post by Jugglerguy on Aug 6, 2016 13:13:39 GMT -5
Thanks everyone. Can someone give me a quick idea of how to stabilize it? I've never stabilized anything, but I have read a little about it in the past. Is there one technique that might work well on this particular stone? If it's something I can do without ordering materials, that would be better. For example, I can run to Home Depot to buy super glue. Is that an acceptable CA glue?
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Tommy
Administrator
Member since January 2013
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Post by Tommy on Aug 6, 2016 14:20:05 GMT -5
Rob - I need to somewhat retract my stabilizing comment above - I don't know if that would really help you with the undercutting issue. If you twist the material in your fingers and it is breaking fairly easy then it's a better candidate for stabilizing.
Heating in Opticon is one option I've done a few times and it works good. There are some pretty straight forward instructions in a tutorial here on the board somewhere. The other common and effective method is to glue it to a backing material that doesn't allow it to break on you.
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Post by Jugglerguy on Aug 6, 2016 14:36:18 GMT -5
Rob - I need to somewhat retract my stabilizing comment above - I don't know if that would really help you with the undercutting issue. If you twist the material in your fingers and it is breaking fairly easy then it's a better candidate for stabilizing. Heating in Opticon is one option I've done a few times and it works good. There are some pretty straight forward instructions in a tutorial here on the board somewhere. The other common and effective method is to glue it to a backing material that doesn't allow it to break on you. Ok, that's not the problem, it's holding together really well. I'll try to skip some wheels as you suggested. Thanks, that's the type of advice I was looking for. I might also try hand polishing a little.
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Sabre52
Cave Dweller
Me and my gal, Rosie
Member since August 2005
Posts: 20,487
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Post by Sabre52 on Aug 6, 2016 16:49:24 GMT -5
Using really worn wheels or belts helps too. Fresher the surface of the wheel etc the worse the undercutting in my experience. I set my soft or mixed hardness cabs aside until my wheels are about shot....Mel
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Post by Jugglerguy on Aug 6, 2016 18:48:46 GMT -5
Using really worn wheels or belts helps too. Fresher the surface of the wheel etc the worse the undercutting in my experience. I set my soft or mixed hardness cabs aside until my wheels are about shot....Mel My wheels are pretty close to brand new. What you say makes sense because the new wheels are bumpy. I have the old wheels that came with the machine, so I'll pop those on before I try again. Thanks!
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Post by fernwood on Aug 6, 2016 20:30:46 GMT -5
Love the color combo.
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Post by rockjunquie on Aug 11, 2016 13:52:19 GMT -5
I cabbed an expensive pietersite with new wheels and had hellish undercutting. After my wheels were well broken in, I went back through the wheels starting with a light touch on the 220 hard. After that, it was smooth sailing and the undercutting was eliminated. So, from this experience and others like it, I say well worn wheels are the way to go- at least, for a first go round.
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QuailRiver
fully equipped rock polisher
Member since May 2008
Posts: 1,640
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Post by QuailRiver on Aug 11, 2016 15:10:06 GMT -5
That's a very cool looking material! The brick red colored conglomerate matrix really compliments the blue Chrysocolla!
As far as stabilizing, one option might be to final shape the cabs and then before sanding use the epoxy/acetone soak method. I personally haven't used this method but have seen several posts on turquoise sites of people who do. I copied one such post but have forgotten who the original poster was so my apologies to the OP. But here it is.
"Epoxy type: 330. Two parts, one hardener, one resin. Water Clear Epoxy. Acetone: One Pint.
Mix both tubes into Acetone, real well. Allow stones to steep for 7-10 days. Swirl brew around about every other day (don't know why, but that's what it says!). Remove and let set for a minimum of one week prior to cutting.
Keep the jar sealed and it will last quite a long time. KEEP IT SEALED! And in an area that's cooler than my back yard during the month of July. Places NOT to keep it; near the water heater or other sources of heat that could emit either sparks or open flames (acetone is very combustable), where the children can find it...
Remove stones from soup. (Kitty litter scooper works good as long as the mouth of the jar is wide enough, and it's not currently being used for it's designed task.) Place extracted stones on a surface that no one's going to mind if it gets a little crudded up (wife's china, DON'T DO IT!). Let dry another week."
The original OP didn't mention this but nearly every other turquoise stabilizing formula I have seen requires drying the stones out well in an oven at around 180 degrees F right before treating to force moisture out so that the resin will be better absorbed.
Larry C.
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Post by orrum on Aug 11, 2016 17:39:52 GMT -5
Always soak the copper minerals first overnite in water b4 slabbing or cabbing or trim sawing Rob.
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Post by orrum on Aug 11, 2016 17:44:45 GMT -5
Rob I rough shape on a 220 SC hard wheel. The finish shape on a 400 SC expando belt. Then a plumb wore out 600 SC belt. Then sapphire powder on a buff. Then Zam on a buff. Then wipe with a clean cloth to get fuzzys off.
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Post by Jugglerguy on Aug 11, 2016 21:38:33 GMT -5
That's a very cool looking material! The brick red colored conglomerate matrix really compliments the blue Chrysocolla! As far as stabilizing, one option might be to final shape the cabs and then before sanding use the epoxy/acetone soak method. I personally haven't used this method but have seen several posts on turquoise sites of people who do. I copied one such post but have forgotten who the original poster was so my apologies to the OP. But here it is. "Epoxy type: 330. Two parts, one hardener, one resin. Water Clear Epoxy. Acetone: One Pint. Mix both tubes into Acetone, real well. Allow stones to steep for 7-10 days. Swirl brew around about every other day (don't know why, but that's what it says!). Remove and let set for a minimum of one week prior to cutting. Keep the jar sealed and it will last quite a long time. KEEP IT SEALED! And in an area that's cooler than my back yard during the month of July. Places NOT to keep it; near the water heater or other sources of heat that could emit either sparks or open flames (acetone is very combustable), where the children can find it... Remove stones from soup. (Kitty litter scooper works good as long as the mouth of the jar is wide enough, and it's not currently being used for it's designed task.) Place extracted stones on a surface that no one's going to mind if it gets a little crudded up (wife's china, DON'T DO IT!). Let dry another week." The original OP didn't mention this but nearly every other turquoise stabilizing formula I have seen requires drying the stones out well in an oven at around 180 degrees F right before treating to force moisture out so that the resin will be better absorbed. Larry C. Thanks Larry. I'm not sure I willing to put in quite that much effort yet, but I'm going to save this for possible use in the future. My second attempt was better. I'm going to keep trying!
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Post by Jugglerguy on Aug 11, 2016 21:39:27 GMT -5
Always soak the copper minerals first overnite in water b4 slabbing or cabbing or trim sawing Rob. Why?
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Post by orrum on Aug 11, 2016 22:10:20 GMT -5
Don't know how it actually works Rob but it helps the thing be stable and not crumble and undercut as bad. Also I back all of this group just like turquoise with Devcon Steel reinforced epoxy. Spread it on wax paper and gently push the slab down innit and then after it sets use the trim saw like normal. If cabbing with a Genie put both spritzer under the wheel. Use Devcon, the others don't compare.
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