rocpup
spending too much on rocks
Pink Limb Iris
Member since March 2011
Posts: 465
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Post by rocpup on Mar 22, 2011 12:43:55 GMT -5
About ten years ago we found a virgin rock area about twenty miles from Yuma AZ. The agate-jasper was mostly float and we have not yet done any digging. Much if not all of the material found there, like most areas, is very unique. The variety seems endless. We collected several hundred pounds and are still cutting surprises. The one I want to talk about this time is a rock that can not be cut with a diamond rocksaw. I put the rock pictured in my old 14 inch Hiland-Park. The saw labored through the rock but did cut off. I moved the carriage over to cut a slab and walked away as usual. When I returned the drive belt was burnt in to. I checked the rock and it had not slipped in the vise. I replaced the belt and this time I watched to see what the problem was. The rock engaged the saw and started to howl from the pressure the feed was putting on it. I have cut hundreds of rock and never have found one like this. After inspecting the blade I found there was no diamond present. I put a similar rock into a different rock saw and watched it try to cut it. The saw made it about half way through and started to howl. Another inspection also found no diamond on the surface of that blade. It took a lot of cutting through a grindstone to get the blades to cut agate again. I sent a very small piece out to be analyzed. The information that came back was as follows. Major: silica, manganese oxide and manganese silicate. Accessory: barite (baryum sulfate) and calcium-manganese-lead-copper oxide. The material has a black streak and when mixed with agate a hardness near seven. I have no way to check the SG but it is heavy. I concluded the rock was a form of Psilomelane or another guess Romanechite. When this material is present in small amounts with agate it will cut in the saw and cuts a very nice cab. Last week I kinda forgot and put a small rock and it was about half Romanechite. Well again back to cutting grindstone after a couple of cuts but I have a couple of nice slabs to cut. If someone here would like to further analyze this material PM me. Rocpup
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Post by jakesrocks on Mar 22, 2011 13:14:00 GMT -5
Sounds to me like the metalic content of the rock is glazing the blade. There is a special blade made to cut high metalic content rocks. I have the info in a catalog here somewhere. When I find it, I'll post it here. The blade is used for slicing meteorites. Don
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quartz
Cave Dweller
breakin' rocks in the hot sun
Member since February 2010
Posts: 3,352
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Post by quartz on Mar 22, 2011 13:20:30 GMT -5
A fellow club member was growling about having some rock so hard he couldn't cut it, I don't remember what it was. He said he was using mineral oil in the saw. I offered that we use hydraulic oil in ours [two 16's] and have yet to find something that wouldn't cut. At the next meeting, he said he cleaned the saw and put hydraulic oil in it, and it cut just fine. Not much at analyzing, but what coolant are you using? Opinion: That would be the first thing to look at.
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Post by Jack, lapidaryrough on Mar 22, 2011 13:41:40 GMT -5
our a rounded saw blade, on the cutting face needs to be flat Squared. to the cutting surface
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rocpup
spending too much on rocks
Pink Limb Iris
Member since March 2011
Posts: 465
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Post by rocpup on Mar 22, 2011 13:45:57 GMT -5
Yes I have also heard there is a blade designed for cutting this type of rock but at this point there is three blades hanging on a nail to replace the ones in my saws. I am not much on believing changing oil is going to make a difference. I use Pella A in the Highland Park and Antifreeze in the Hillquest. The rock pictured is 6x6x4 inches and weighs eight pounds.
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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 Mar 22, 2011 14:18:02 GMT -5
Yep, metallic ores will mess up a blade. Too much drag and too much glazing. Siskayou Stone which consisted of metallic ores in quartz can do the same thing if it's a big hunk....Mel
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Post by johnjsgems on Mar 22, 2011 14:54:00 GMT -5
CBN is the name of the meteor blades. Yours looks like boytroidal psilomalene or hematite and like Mel said it likely glazed the blade. What you saw as no diamond was the metallic material in the rock covering the diamonds.
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Post by akansan on Mar 22, 2011 15:13:10 GMT -5
I have seen cabs from boytroidal psilomalene, so would love see full slabs from this!
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rocpup
spending too much on rocks
Pink Limb Iris
Member since March 2011
Posts: 465
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Post by rocpup on Mar 22, 2011 15:15:08 GMT -5
I agree with that conclusion. To invest in a CBN meteor blade maybe worth it with the price of Psilomelane and Romalechite mineral samples but I do not have a market for it. I have about a hundred pounds of this material if someone is interested.
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Post by deb193redux on Mar 22, 2011 16:09:16 GMT -5
I just bought a 2lb piece of boytroidal psilomalene. I hope it does not prove too difficult to cut.
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