showet
Cave Dweller
Member since June 2015
Posts: 65
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Post by showet on Aug 18, 2015 10:27:55 GMT -5
I am still learning and trying to not make too many mistakes so I have a question. When we are choosing rocks to tumble together how similar does the hardness need to be? for example can Mohs 6 (Labradorite), Mohs 6.5 (Mexican Lace agate) and Mohs 7 (quartz) be tumbled together or should they be tumbled separately? I know you would not want to tumble a 4 with a 7, but what about a 6 with a 7?
Is it the same for all stages?
Is it the same for rotary and vibratory?
Thanks for any help with this I want to get the best result without wasting rocks experimenting if possible.
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tkvancil
fully equipped rock polisher
Member since September 2011
Posts: 1,547
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Post by tkvancil on Aug 18, 2015 10:44:07 GMT -5
Hardness isn't the only determining factor in what can be tumbled together. It is probably the first though. I do locally collected feldspars (mohs 6) with agates (mohs 7) and they do alright. I tried it with labradorite, another feldspar, and they got beat to heck. Different crystal structure I suppose. As to labradorite it is best done by itself, although I have mixed it with sodalite and obsidian without issue. The crazy lace will roll well with any other agate, at least always has for me.
Generally if the hardness is the same or a difference of .5 to 1 they will do alright. The softer ones may grind faster.
Best advise for a first tumble is agate or jasper. Keep hardness the same and get that experience before moving on to anything soft.
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showet
Cave Dweller
Member since June 2015
Posts: 65
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Post by showet on Aug 18, 2015 10:50:28 GMT -5
Probably good advice. Since I was about 5 I kept getting the advice "wait and get that experience before moving on". There must be something to that!
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Shelbeeray
has rocks in the head
Member since January 2006
Posts: 688
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Post by Shelbeeray on Aug 18, 2015 15:35:09 GMT -5
I generally tumble the same kind of rocks in each batch, i.e. agates in one batch, quartz in another, jasper in another.... My tumbles turn out better that way. Some are more prone to fracturing and pitting. Kind of depends on the stones included.
Labradorite is pretty picky and easily fractured, even more so than quartz. If you are tumbling that, I'd do it alone and with plastic pellets for cushioning, which is what I also use for quartz. I don't use pellets for agates or jasper. In my experience, the three you mentioned should be tumbled separately for best results.
It would be worth your while to look up the structural differences between the three types you mentioned - agate, labradorite and quartz. They are very different and respond differently.
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stonemaster499
noticing nice landscape pebbles
Member since July 2014
Posts: 97
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Post by stonemaster499 on Aug 18, 2015 20:33:25 GMT -5
Hardness is one point, and as Shelbeeray and explained also important to consider structure - cleavage is more important compared to hardness when it applies. Stones with cleavage break along structurally weak planes in the crystal structure. This could mean hell in your final stretch - say 1000 stage, one rock cleaves, and contaminates the entire batch... Labra has 2 directions of cleavage! This means its not appropriate for a beginner. It can be tumbled fine with similar stones in hardness 5-6.5. This will not lower the quality. I would agate media for smalls (mixed ceramic media is fine), soap, SLOW down the tumbler, add a thickening agent to prevent the stones from banging, and finish in a dry vibe polish.
I would mix agates and chalcedonies (ie jaspers too). Quartz separate. and not mix the labra with the others mentioned. another reason for not mixing those 3 groups is different processes, speeds and cycle times. And shoet, please read one of the guides first, in the event you haven't already. Kinda hard to screw up, as you can always go back and forwards (with steps) and this is how you will learn. good luck!
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