Deleted
Deleted Member
Member since January 1970
Posts: 0
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Post by Deleted on Nov 10, 2008 18:13:39 GMT -5
Hi all,
I have some large chunks of obsidian that I would like to reduce to smaller chunks. The reason being, my 10" saw is not set up and so I only have a 6" saw to work with for the time being. Some of this obsidian is rainbow.
If I were to try to break up some of this material, would I end up with mainly usable small chunks that could then be cut with my trim saw to orient color? Or would I end up with a pile of worthless shards? I realize I would end up with some tiny pieces but if I ended up with mainly small chunks, I would be happy.
Im asking this on the tumbling forum because I figure the tumblers have more experience with busting up material. If this idea would work, how would I safely go about it? Crack hammer? Chisel and rock hammer?
Thanks,
Shannon
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Sabre52
Cave Dweller 
Me and my gal, Rosie
Member since August 2005
Posts: 20,496
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Post by Sabre52 on Nov 10, 2008 18:33:07 GMT -5
Boy, I've done it and it's pretty messy and I got a lot of waste. I was really not to happy with the results. Obsidian is both brittle and tends to break into flakes that are kind of thin. Lots of nasty tiny very sharp flakes too. I'd wrap it well in some kind of smooth cloth like maybe an old pair of jeans. Towels and stuff just hold too many fine and dangerous slivers. Wear gloves and eye protection and I'd use a lighter hammer rather than a cracking hammer. I cover what little hair I have too because I've even had tiny slivers land in my hair and fall out later. Man, I'd hate to have one fall in my eye! I found it breaks best with calculated softer blows and taps, rather than really whacking it. My stuff is mainly in nodules and doesn't have much in the way of fracture lines along which it might break more easily. A different type might be easier to work. Overall, I can't say it's one of my favorite materials to break up for tumbles or smaller cabbing material.....Mel
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lparker
fully equipped rock polisher
Still doing too much for being retired!
Member since March 2008
Posts: 1,202
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Post by lparker on Nov 10, 2008 18:48:15 GMT -5
I wouldn't use a steel hammer. It tends to put a lot of micro fractures in obsidian. If you haven't spalled out any nodules before, you WILL end up with what Mel said. Use a copper hammer, or find someone with a larger saw. Best thing to do is hang on to it until the larger saw is up and running...especially for the rainbow.
Lee
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Post by johnjsgems on Nov 10, 2008 20:55:02 GMT -5
I think Lee nailed it. Put it aside for now. Obsidian is volcanic glass and will break like glass. Rainbow is too nice to waste in my opinion.
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drjo
fully equipped rock polisher
Honduran Opal & DIY Nut
Member since May 2008
Posts: 1,581
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Post by drjo on Nov 10, 2008 21:39:54 GMT -5
You could cut slots (slab thickness apart) in it with the 6" saw and then hit it with a dead blow hammer or use a wooden wedge in the saw slot and hit the wedge with the hammer.
Dr Joe
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Post by bobby1 on Nov 11, 2008 0:06:09 GMT -5
Shannon, Here is a 20 lb piece that my grandson "tapped" with another rock. It had been sitting in my yard for years and I knew it had some green fire that I saw in it when I collected it. It broke into about 6 larger pieces and quite a few smaller pieces including small shards. I wasn't aware of how bright the green was until then. I think he hit it with a rounded piece of jasper.    The pieces were very random in shape, but few ended up with fractures. I would think if you whacked it moderately with the rounded end of a ball pein hammer that concentrated the force in a small point that you could be randomly successful in getting a usable sized piece. I would recommend doing it outside and with a heavy duty cloth draped over it. Bob |
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Post by deb193redux on Nov 11, 2008 1:47:07 GMT -5
thats nice gree obsidian.
I also vote for the cut some slots and hit with a chisel.
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Post by akansan on Nov 11, 2008 22:22:02 GMT -5
I like the idea of being randomly successful. Can I be randomly successful in life?
I also vote for the notches and chisel.
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Post by Hard Rock Cafe on Nov 11, 2008 22:52:57 GMT -5
Bobby, that looks like a happy accident to me. That is spectacular color.
Chuck
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rollingstone
starting to spend too much on rocks
Member since July 2009
Posts: 236
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Post by rollingstone on Nov 12, 2008 2:08:44 GMT -5
Interesting thread, as my experience with obsidian seems quite different than some other people's. I wasn't breaking up really big chunks so maybe that makes a difference, I was breaking up smaller chunks into tumbling size. I used a hammer and chisel and found that soft hits just made the obsidian spall off in thin unusable shards. Hard whacks broke it really cleanly, exactly where I wanted, with very little waste.... obsidian is probably the nicest material to bust up I have encountered. So based on my experience, I'd say notch it with a saw if that will help set the chisel, then use a cold steel chisel and strike the chisel as hard as you can with a good heavy crack hammer.
-Don
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Post by krazydiamond on Nov 13, 2008 16:08:58 GMT -5
this is very interesting, as i also have a tub of larger than saw sized pieces of snowflake obsidian, but have been afraid to whack it up for tumbling because of the shard problem. i might try the notch and cold chisel method, thanks!
KD
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