Lapidaryforum.net
Rock Art => Cabochons, Intarsias, Cameos => Topic started by: drnihili on April 20, 2015, 01:07:48 PM
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This is the one I'm working on now. Who knows, maybe I'll finish it. Thus far I have a habit of working on something until it's almost done and then abandoning it. We'll see, we'll see ....
It's about 2 inches long with a concave (8 inch radius) back from side to side that is slightly convex end to end. That soundsmore complicated than it is, but I'm trying to be evocative of the cobble I found it as. What appears as checking in the photo may be a trick of the light as I can't find it on the stone.
Comments welcome, identification requested. (Found on Deer Creek, Frank.)
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Those darn closeups find the darndest thing :) It's looking good :headbang:
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I worked on it some more and, oddly, going from 3000 to buffing actually took the shine off. I put some time on the 14k belt and got it back though. Unfortunately there are some scratches and undercutting remaining. They're only visible with a loupe, and close up shots, but they annoy me.
I'm wondering about dropping back to 1000 and proceeding forward more slowly. Thoughts?
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Meh, the actual color is somewhere between the two. Teresa says the light areas are "sagey mint", the darkest areas are essentially black.
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Its still looking pretty good but I hate to say it, it looks like you are getting some orange peel now :( It happens some times if you work the stone too much
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Yeah, I am. How does one rectify the situation?
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A stone that has exhibited orange peel ( differential cutting rates ) should never go to a felt or muslin buff. That said there are people deft enough to use a muslin buff to advantage with these stones but the buff is partially deconstructed to keep it soft ( stictching partially removed) and it is used in an extremely light manner. A more conventional approach is to use the last aggressive belt that cuts both the soft and hard components evenly then try 14,000. It may go from 1200 or 3000 diamond to the 14,000. The same concept was used with sic by hoarding and using very worn 600 grit belts as the pre polish step. The stone has chrome diopside blebs ( green ) and may have in varying proportions vesuvianite , chlorite , diopside , nephrite and /or pumpellyite.
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Thanks, Frank. If I get a chance I'll try moving from the 1k belt straight to the 14k. Our buffing wheel is leather, but this is the second stone I've had issues with. How often does the leather need to be replaced?
I found another piece out on the bar with significant chrome diopside in it, but I'm still puzzling how to cut it.
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Well a somewhat worn 600 SiC belt seems to have helped the orange peel. Following up with the 14k puts a decent polish on the dark portions, but not the lighter portions. I'll try fidgeting around with it more later, but for now I should probably get back to work. Brilliant ideas to try would be welcome.
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A bit more work and here is where I'm at. The orange peel seems to be under control, and there's substantially less undercutting. One of the issues I'm having now is that the chrome diopside doesn't want to take much of a polish. I seem to do best with just a 14k diamond belt. Buffing seems to dull the stone.
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The jump must be too great for the 14,000 to bring the polish up on the chrome diopside. Dry sanding is the usual cure but as you are inexperienced and this is a very distinctive stone I would hold off on that trick. Leather can cause undercutting as well.
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Can I raise my hand and say I think it's beautiful just as it is? :headbang:
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Can I raise my hand and say I think it's beautiful just as it is? :headbang:
LOL
it's never good enough Amanda; we're MEN!!!!!!! LOL
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The jump must be too great for the 14,000 to bring the polish up on the chrome diopside. Dry sanding is the usual cure but as you are inexperienced and this is a very distinctive stone I would hold off on that trick. Leather can cause undercutting as well.
I did notice that dry sanding helped. I agree about setting this aside for a bit. I'm thinking I should grab a hunk of meta-stuff and play around with it, something I have plenty of. I find I'm much more attached to three weird local rocks than to the more traditional stone such as jade. I also need th finish that piece you said was particular granite our some such.
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Can I raise my hand and say I think it's beautiful just as it is? :headbang:
Thanks. The nagging flaws don't show up so much in the photo.
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Setting rocks aside is a time honored stone cutter tradition. A time comes for all stones is my point of view so I go with my inspiration of the moment.I have a stream with very big pieces of oceanic chert to show you , spectacular ones , but mid summer is the time. If you like the oceanic cherts now you will be stunned with these boulders. In the interim I have a spot near Darrington with superb pieces of very unusual oceanic chert in solid red , solid black and solid silver colored.We can get there now most likely and water depth is not an issue. When you would like to go out holler. The coolest hornfels in Washington is up that same road so we should be able to go there as well. The great chert boulders are from the Bell's Pass Terrain if you want to do some reading up .
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Looks good to me. I had someone tell me that on most stones he goes from 1200 straight to cerium oxide on leather. I have yet to try that yet as I haven't finished a cab in well over a week. I was sick and just didn't feel up to going out to the shop. He said optical cerium oxide. I guess that there are differences in cerium oxide but I don't know the differences in how well they polish. I have some from Graves in Florida but it is labeled as their cerium oxide so I have no idea as to the grade. It seems to work well for me though. I have purchased a cab from a master cabochon cutter and I know that he uses cerium and my first comment was that there is just something about his polish. It's not super shiny (it is very shiny) but there is just something about it that makes the cab stand out. Maybe Frank or Lloyd can chime in about this.
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There has been a lot of controversy about cerium oxide quality in the last few years. Before the availability of diamond pads or soft wheels oxide polishes were crucial. Not so much anymore . Rough now is generally not up to the quality of rough of the past , it has more cracks and pits , so oxides are often a problem as they get lodged in the stone and mar it's finished appearance. In addition the diamond has allowed non traditional stones that are not as silica filled to be cut well. Oxides can be deadly fast. They can take a polish a long way quickly but can also be a trap . In the old days we saw many stones with a great polish but inferior sanding. Polish over visible scratches. I have seen this in very expensive stones from Europe ( Idar ) from the late 1800's.
The speculation in rare earths caused by the Chinese manipulation of the market brought a tremendous run up in some oxide prices and cheaper grades seem to have become the norm. This was a trend before the crisis as well. The purity of the oxide and the type of contaminants are crucial. The optical industry used to use a grade labeled " French " I believe and it could be distinguished by color to a degree. I have seen white , pink and yellow cerium over the years. PH can also make a difference as either extreme seems to make polishing easier. Traditionally out west acids were used with cerium. Colloidial polishes used a very basic strategy and it seems to have basically gone by the wayside.If you find polish you love reorder immediately after being assured it is identical to the grade you like. The quality due to source and manufacturing process varies with time.