Henry
spending too much on rocks
Member since January 2013
Posts: 452
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Post by Henry on Feb 5, 2013 16:54:17 GMT -5
I assume that this is beach jasper (nice areas of translucency) with "?" inclusions (quartz, chalcedony??) How many go-arounds in coarse grind would you folks suggest to get the pits and bumps out? Thanks! Attachments:
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Henry
spending too much on rocks
Member since January 2013
Posts: 452
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Post by Henry on Feb 5, 2013 16:55:13 GMT -5
Part 2 Attachments:
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Post by Toad on Feb 5, 2013 18:03:13 GMT -5
Until it is completely smooth. Whether it takes 2 or 10.
Of course other people aren't as picky. You might save some time by grinding out with a dremel tool first to get rid of worst of the pits...
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grizman
freely admits to licking rocks
Member since July 2011
Posts: 878
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Post by grizman on Feb 5, 2013 21:33:30 GMT -5
Until it is completely smooth. Whether it takes 2 or 10. Of course other people aren't as picky. You might save some time by grinding out with a dremel tool first to get rid of worst of the pits... What kind of a bit or drum do you use on your Dremel to grind out pits and flaws? How long would you work on a stone like the one shown?
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jspencer
freely admits to licking rocks
Member since March 2011
Posts: 929
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Post by jspencer on Feb 5, 2013 22:49:16 GMT -5
If I were to tumble something that large (and I do) I`d put it in some 40-60 grit and plan on minimum of a month in that round unless you have a pretty aggressive tumbler. You`ll need to replenish the grit in that time but get them good and round and smooth as you can. First grind is very important to do completely. You`ll be happy you did when it`s all done.
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Post by Peruano on Feb 6, 2013 11:31:10 GMT -5
I'd be tempted to grind away some of the major blims before tumbling. Even a common bench grinder with a SiC wheel will wear at it quickly to the advantage of your tumbling efforts which btw will restore or enhance the polish. You probably can safely arrange a drip of water onto the front of the wheel and a plastic cake pan underneath to catch and contain it if you don't have access to a lapidary arbor. Let your wheel spin off all water before turning it off to keep one side from becoming waterlogged and out of balance. First off we are not sure what the rock is. It may be a quartzite or granite with some inclusions rather than jasper. If it is jasper it may tumble unevenly (i.e. the quartz inclusions may be harder than the jasper matrix). None of this is to discourage you from tumbling it but I'd try to find a similar rock and maybe bash (or saw) a fresh surface on it to see what it will look like when tumbled. If you can get rid of the largest of the blims the tumble will not be so prolonged. If you can get ahold of smaller ones that can be thrown into a mixed load you will get a good idea of how much effort will be justified for the bigger/rougher one. I use a vibrating tumbler, often use rocks previously "preformed" by nature in the surf, and still find it advantageous to grind a bit on them before the tumble. Vibes are much faster and in 4-5 days you will know where you are going and whether it is worth it. Food for thought, I hope. Tom
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