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Post by Peruano on Nov 24, 2012 14:58:53 GMT -5
The Pedernal Chert from NM has many fractures, tries to flake into thin fragile pieces, and is somewhat unpredictable as to whats inside. I tried this in the vibrating tumbler (Raytech) starting out with 120/220 grit instead of something coarser. It ran 24 hrs in 120/220, 24 hrs in 500, and 36 hrs in 800. I have not tried to polish it but decided to show it as is with and without backlight. Back lit Normal sunlight Thicker stuff BTW These were mostly small pieces along the side of the road, most probably broken up by the road grader - no native American products here even tho this formation was a common source of tool material by Anasazi and Pueblo peoples. I have some larger chunks that I'll try to saw up in the future. Thanks for looking. Tom
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carloscinco
fully equipped rock polisher
Member since July 2008
Posts: 1,639
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Post by carloscinco on Nov 24, 2012 17:19:33 GMT -5
That is really nice looking material. If this was a rotary batch I'd say it needed a little more coarse attention.
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jspencer
freely admits to licking rocks
Member since March 2011
Posts: 929
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Post by jspencer on Nov 24, 2012 22:47:09 GMT -5
It`s not recomended to use anything coarser than 220 in your vibe. I`d run them a few days in 220 to knock off some of those sharp edges. Add a handful of small rounded pebbles or pea gravel if you don`t have a ceramic mix to add in to pad the rocks and help smooth these out. I never run any stage less than 2 full days and normally go 4-5 days in 220 stage if not smoothed first in a rotary first. It`s all about surface contact in polishing.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,184
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Post by jamesp on Nov 24, 2012 23:59:58 GMT -5
That is attractive high grade chert.
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The Dad_Ohs
fully equipped rock polisher
Take me to your Labradorite!!
Member since September 2012
Posts: 1,860
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Post by The Dad_Ohs on Nov 25, 2012 0:13:51 GMT -5
I agree with jspencer, more time in the 220 is needed... and also something to remember, if this stuff was run over by a grader or compactor it probably has internal fractures that will come out as you tumble, so don't be too surprised to see them after a batch has tumbled.. it just means that you will have to go longer to get them out ... or cut/grind them out b4 tumbling any further.
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