karenfh
fully equipped rock polisher
Member since November 2006
Posts: 1,495
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Post by karenfh on Dec 3, 2006 4:26:40 GMT -5
I've got a chunk of pet wood that I've tumbled twice, now. Put it in the first hard grit, and then the second stage fine grit, hardly made a dent. So I held it out, and put it in again in the first 2 stages of my next batch. Still looks pretty much the same after almost 12 weeks total tumbling. You can hardly tell that it was tumbled! Had a few other pieces of pet wood, they did shape up nicely. Are some pieces harder (!!) than others? If so, what do you do with the really hard pieces??
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Sabre52
Cave Dweller 
Me and my gal, Rosie
Member since August 2005
Posts: 20,494
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Post by Sabre52 on Dec 3, 2006 13:44:13 GMT -5
karenfh: The books say most petrified wood is Mohs hardness 6 1/2-7 which would be in the same range as the rest of the jasper and agate. Some of course is replaced by barite or calcite and is much softer. I'm with you though, some of the wood, when I tumble or saw it, seems much harder. Only thing I can guess is the harder bits are the more silicified while the softer are less so and maybe contain more of the softer mineral salts......mel
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madgg
starting to shine!
Member since February 2005
Posts: 39
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Post by madgg on Jan 7, 2007 9:46:56 GMT -5
I've found pet wood that is completely ground away when tumbling, and other pieces that tumble forever and never seem to smooth up. I agree with Mel. I think it depends on what minerals formed the wood! Colleen
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blarneystone
spending too much on rocks
Rocks in my head
Member since March 2010
Posts: 307
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Post by blarneystone on Jan 7, 2007 10:56:07 GMT -5
....Put it in the first hard grit, and then the second stage fine grit, hardly made a dent. So I held it out, and put it in again in the first 2 stages of my next batch?... It sounds like it's not getting enough time in 60/90... My experience has been that 120/200 doesn't remove much material on stones harder than moh's 6 ...it only removes the large scratches left by the 60/90 grit. Do you re-charge your 60/90 stages every 7 days? |
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Post by deb193 on Jan 8, 2007 20:05:05 GMT -5
I think that density is independent of hardness. SOme agate is a lot more dense. I cut some Arizona pet wood recently that I had to slow down my autofeed to 1/8 speed.
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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 Jan 9, 2007 2:52:41 GMT -5
It sounds like it's not getting enough time in 60/90... My experience has been that 120/200 doesn't remove much material on stones harder than moh's 6 ...it only removes the large scratches left by the 60/90 grit. Do you re-charge your 60/90 stages every 7 days? I agree. Let it run for a week or so each time in 60/90, then completely clean things out and add new grit and go again. Nicely silicified petwood will take 4-6 weeks to shape up well in coarse grit. Don't move it to fine grind (120/220) until you are finished coarse grinding, as fine grind will not shape the material in any noticeable way, it just starts it on the road to a nice polish. -Don |
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stefan
Cave Dweller
Member since January 2005
Posts: 14,113
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Post by stefan on Jan 22, 2007 12:53:40 GMT -5
I run a lot of pet wood- Some of it runs for 16 WEEKS in 60/90 alone!!!! Yes some pet wood seems a lot denser than others- but it is not uncommon for me to leave pet wood in for a LONG course cycle!
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MichiganRocks
starting to spend too much on rocks
"I wasn't born to follow."
Member since April 2007
Posts: 154
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Post by MichiganRocks on Jan 22, 2007 20:31:21 GMT -5
Pet wood is completely dependent on what minerals were deposited in the original wood. If the wood was thoroughly replaced by quartz (with different minerals for color), then it will be HARD. I recently ran some pet wood from NM and I ran it all summer to get it right. If that's what you're running, then be patient. Wait it out, let it run. You'll be happy you did!
Ron
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spacegold
has rocks in the head
Member since September 2006
Posts: 732
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Post by spacegold on Jan 23, 2007 0:31:10 GMT -5
Another difference that has not been mentioned is the difference between opal and agate replacement of the wood. Opal is a hydrated silicate that is softer than unhydrated quartz. But you can't tell the difference by looking at the stone. The difference shows up quickly in the tumbler. Opalized wood rounds out fairly quickly in the coarse drum. Agatized wood is much slower and requires a lot of time and patience in the 60/90.
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stefan
Cave Dweller
Member since January 2005
Posts: 14,113
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Post by stefan on Jan 25, 2007 13:49:24 GMT -5
A lot of pet wood problems have to do with the replacement itself- the "replaced tree rings" offer a good fracture point- and this often leads to the frustration with it- it seems to keep breaking apart and "chunking up" Hang in there- it will settle down and behave-
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