johnnyu
starting to shine!
Member since January 2011
Posts: 27
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Post by johnnyu on Feb 25, 2011 16:55:46 GMT -5
Just wanted to show a couple of pieces I've been using to learn about polishing. I've got a long way to go but I really enjoy polishing pieces in their natural shapes. Any thoughts on how to improve would be appreciated. I'm currently using a variable speed 4" rotary polisher w/water and diamond pads from 60 grit up to 6000 grit. Jade from North Cascades: Close up: Serpentine (thought it was jade until I put a magnet to it): And the other side of this one: Any thoughts on how to get better at polishing would be appreciated! Johnny U
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mossyrockhound
fully equipped rock polisher
Member since January 2011
Posts: 1,278
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Post by mossyrockhound on Feb 25, 2011 23:41:09 GMT -5
That jade looks pretty good to me. I didn't know serpentine was magnetic. I've got some I'll have to check out. Garry
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johnnyu
starting to shine!
Member since January 2011
Posts: 27
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Post by johnnyu on Feb 26, 2011 1:25:42 GMT -5
Hi Garry:
One of the tricks I use to distinguish Jade from Serpentine is by using a tiny neodymium magnet (from Radio Shack). These rare earth magnets are about 2 millimeters across and 1/2mm thick - extremely small but VERY strong. I keep this tiny magnet in a ziploc bag. I then will touch the bag/magnet to the surface of the rock and pull it away - if there is any hesitation to the bag pulling away it isn't jade. (A wet rock will act the same way due to the surface tension of the water - be sure the rock and bag are both dry for this test). All sepentine I've found in the N. Cascades will indicate magnetic properties with this test. I've heard some serp is completely non-magnetic but I've never seen any.
Johnny U
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Post by bobby1 on Feb 27, 2011 0:44:33 GMT -5
Usually a simple scratch test with a pocket knife will separate the soft Serpentine and its cousins from Nephrite. Bob
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Post by rockrookie on Feb 27, 2011 8:32:52 GMT -5
wow !! those are big peices . Very cool ! --paul
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wyobrian
fully equipped rock polisher
GO VIKINGS
Member since February 2009
Posts: 1,739
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Post by wyobrian on Feb 27, 2011 11:55:00 GMT -5
Nice find !!!!
Brian
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Sabre52
Cave Dweller
Me and my gal, Rosie
Member since August 2005
Posts: 20,466
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Post by Sabre52 on Feb 27, 2011 13:39:41 GMT -5
Interestingly enough, much of the California jade contains inclusions of magnetite and high concentrations of iron so it is magnetic. I've got Porterville jade that a kitchen magnet will stick to with ease. The hardness test is always the best bet for jade....Mel
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MikeS
fully equipped rock polisher
Member since January 2009
Posts: 1,081
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Post by MikeS on Feb 27, 2011 14:14:54 GMT -5
Making an ID on jade can be tricky. The scratch test is a good initial test, but I have seen lower grade nephrite that will scratch a bit if you scratch it on the weaker oxidation rind or if it has a high level of forigen inclusions, or has areas of a less compact grain structure near the surface. The magent isn't foolproof either, as some jade specimens can actually have magnatite inclusions in them as well, depending on the region they were collected. Specific gravity is a good test as well, but again, some nephrite can have a slightly lower SG based on purity of the material.
One of the fastest ways to initially evaluate it is to look at the break (if the specimen has one). Nephrite jade has a unique looking break, best desribed as what a piece of fudge or cheese would look like broken in half. It has a somewhat "flakey" looking grain structure. Generally, the smaller and more compact the flakes appear, the higher quality the jade. Another quick field test is the old timer's rock hammer test...high quality jade will "ring" when struck with something metallic, where serpentinite will just make a "thud" noise....
I know, not real scientific, but when all these are combined, you can get a good idea if you have a piece of jade or not....
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Sabre52
Cave Dweller
Me and my gal, Rosie
Member since August 2005
Posts: 20,466
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Post by Sabre52 on Feb 27, 2011 18:32:51 GMT -5
Yep, the ring tone is one of the ways we hunted jade up at Porterville. A big hunk of jade will ring like a bell.....Mel
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stefan
Cave Dweller
Member since January 2005
Posts: 14,095
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Post by stefan on Feb 28, 2011 14:15:52 GMT -5
Nice stuff! As for your polishing- any reason why you can't go higher than 6000? I would think that a leather pad and some diamond paste in the 14k and 50 k would real bring out the shine (although at 6000 that shine is pretty stellar!)
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