dsmith14469
noticing nice landscape pebbles
Member since May 2009
Posts: 82
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Post by dsmith14469 on May 12, 2009 12:20:33 GMT -5
My vacation down to Tennessee and North Carolina got me reinterested in rock tumbling. I went to one of the garnet mines in NC and sluiced the dirt. One rock I found was a dodecahedron garnet. I finished the rough tumble on this and other stones of equal MOH but it didn't seem to change any. Is this more of a faceting crystal, or is there nothing much that I can do with it?
Thanks
Dean
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Rogue Trader
freely admits to licking rocks
"Don't cry because you are leaving, smile because you were there."
Member since December 2008
Posts: 839
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Post by Rogue Trader on May 12, 2009 12:54:56 GMT -5
Dean, Garnets are very hard materials that is why they are used in the making of abrasives and emery papers/clothes. Therefore they will require more grinding than your average stone/rock because of their hardness. I recently received a supply of these, and because I was unsure about them I sent one to Mr Peter Tandy, the Curator of Minerals at the Natural History Museum in London, England. This is a part of his reply to me: I received your specimen today and have had a quick look at it. In simple terms I can tell you that it is almost certainly an altered garnet crystal. The exterior shape, although a bit rough, is very typical of garnets (geometrically it is a rhombic dodecahedron). The exterior is altered to a mixture of dark mica (probably biotite mica from its colour) and a green scaly mineral which I can’t really identify by eye, but which might be a member of the amphibole group of minerals. Garnet is a hard material (hence its use in emery paper and abrasives). He suggested, that if I were to use them for tumbling, it would take a longer period than usual, and that it might (to me) seem as if they (the garnets) were not progressing. Apart from that there isn't really much more I can tell you. They will eventually start to change, but for the moment I'm just using them as a hard filler abrasive in my normal tumbles. Sorry to have been of no use to you whatsoever. I'm sure someone will be along soon to pooh pooh my comments.  |
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dsmith14469
noticing nice landscape pebbles
Member since May 2009
Posts: 82
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Post by dsmith14469 on May 12, 2009 13:09:26 GMT -5
Thanks, any bit of information help. The smaller pieces of garnet that I had in there cleaned up nice and smooth, it was just this Dodecahedron that had me puzzled. I put it back in with my next lot of stones and will it run. Well see if anything happens to it in another week.
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docharber
has rocks in the head
Member since October 2008
Posts: 716
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Post by docharber on May 16, 2009 16:01:04 GMT -5
I ordered some almandine drystals as a curiosity for my son's scout troop as part of their Geology merit badge work session. I ordered themn from Tennesseevalley minerls on ebay (Knoxville, TN) by the pound. I had lots left over and decided to run them as filler in a load. Well, they polished some, but were very tough customers and wore down only very slowly. they were not gem quality by any means, and a few cleaved as they tumbled. I think they could take the place of ceramic medi for the same price. They are iron containing and fairly dense. They tended to sink to the bottom in my vibe. Their smooth surfaces didn't hold grit and they were easy to clean. I might order more just as tumbling media.
mark H.
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garock
fully equipped rock polisher
Member since February 2006
Posts: 1,168
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Post by garock on May 20, 2009 16:43:00 GMT -5
Mr. Dean: My uncle found some almandine garnets on Lake Martin in Alamama and and it took him nearly 4 months to get them to polish. They did have a nice shine. So it does take quite a while !! Hope this helps !!
Still Digging in the Dirt, Frank (GaRock)
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