Prov
starting to spend too much on rocks
Member since March 2020
Posts: 116
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Post by Prov on Jun 21, 2020 17:48:06 GMT -5
Saw that other thread about rotary tumbling banded amethyst, and as a coincidence, that's exactly what's in my rotary right now for coarse step. I'm torn on whether I want to put the first batch back in for another week. Looks like they did a lot of chipping while they were turning. If I do put them in for another week, is this the time to start adding some extra sugar to pad them out while they round?
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Prov
starting to spend too much on rocks
Member since March 2020
Posts: 116
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Post by Prov on Jun 23, 2020 23:15:39 GMT -5
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pizzano
Cave Dweller
Member since February 2018
Posts: 1,390
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Post by pizzano on Jun 23, 2020 23:38:43 GMT -5
That recent "other thread" you're referring to pretty well explains the common issues with crushed rough Amethyst being rotary tumbled.........what you have in your hand is typical and common rotary grinding results. Sugar won't stop the collisions in a rotary, which will continue causing the fractures with this material. There are sacrifices that must be made when rough grinding the 1st & 2nd stages. Yes, a good slurry build-up is required, and if you add plastic pellets, ceramics, resin tumbling media to cushion the banging, the rough stages will take much longer, wear out the media and there will still be signs of undercutting since the bands of white between the blue is softer, eventually exposing any internal fractures the material suffered while being crushed as/for tumbling rough..........it's the nature of that material..........sorry for the "negative" feedback, but it is what it is.........a vibe tumbler handles this material much better.
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lordsorril
freely admits to licking rocks
Member since April 2020
Posts: 766
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Post by lordsorril on Jun 24, 2020 5:59:46 GMT -5
Based on your first picture: I would not add those stones to a vibratory tumbler yet because there are still too many flaws. A vibe will round edges and polish, but, is not great at sculpting. I agree with Pizzano that a vibe is the best way to finish this rock.-it likes to chip *a lot*. For shaping this type of amethyst in a rotary I use a mix of small quartz aquarium gravel (pre-rounded with 46/70) and plastic pellets at about a 50/50 mix and fill the barrel 3/4 full. The plastic pellets weigh nothing so you wouldn't need to be concerned about the weight limit on the barrel. I will also throw in a few small sacrificial low mohs rocks that I have rounded previously in other batches (no sharp edges) and this will wear down creating an increasingly thick slurry over time. Final product won't be perfect, but, a few errant small chips can be buffed out by a vibe tumbler. Note: This method only works for me on shaping amethyst pieces the size of your fist or smaller, heavier/larger pieces have different rules.
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Prov
starting to spend too much on rocks
Member since March 2020
Posts: 116
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Post by Prov on Jun 24, 2020 9:24:49 GMT -5
Thanks for the concrete suggestions, I'll work on that. Good to know this expected and how to work with that.
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Post by greig on Jun 24, 2020 14:59:14 GMT -5
If it were me, I'd run these rocks in stage 2 for an extended time with extra grit. Make sure to remove all of the really small chips from stage 1. Something I have tried (I think with success), is to overload the barrel a little bit above 3/4 so the rocks don't crash into each other. More important is listen to it when running, to see if you hear the rocks bumping, especially if they wear down too much from the rough shape as they round ... resulting in a 1/2 full barrel. Any rocks with a deep fracture can be cut or grind it off. Just my two cents
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islander
off to a rocking start
Member since May 2020
Posts: 15
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Post by islander on Jun 24, 2020 15:11:25 GMT -5
I've used my Dremel with a diamond burr to smooth and deepen the sides of a pit or fracture so that it ends up as a regular dished feature. That's usually after stage 1.
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Prov
starting to spend too much on rocks
Member since March 2020
Posts: 116
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Post by Prov on Jul 5, 2020 11:40:08 GMT -5
Whelp, we had a power surge yesterday and the rotary is fried. It was an offbrand lortone, from ages ago that we got from our local lapidary supplier for a total steal price. I think I'm going to purchase a Lortone 33B to replace it. Should speed things along being able to run 2 batches of rock at once to fill the vibe.
Definitely appreciate the suggestions, yesterdays clean out looked better than the first. A lot less chatter. Unfortunately the surge fried it a few hours after clean out. So I got to do it twice.
Looks like my rock tumbling is on hold for the foreseeable future.
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pizzano
Cave Dweller
Member since February 2018
Posts: 1,390
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Post by pizzano on Jul 6, 2020 2:55:27 GMT -5
Sorry to hear about the set back.........more time to collect some new material while waiting....!
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SirRoxalot
freely admits to licking rocks
Member since October 2003
Posts: 790
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Post by SirRoxalot on Nov 18, 2020 23:56:43 GMT -5
I have collected and tumbled a lot of amethyst. There are white lines of two kinds in your material. One is natural color zoning, causing the chevrons. The other is cracks. The cracks mostly need to be done away with before tumbling. The piece in your second photo is an example of potential disaster. Tap it with a hammer and you will see it fall apart into individual intergrown crystals those are the ones that will wait until the polish stage to throw a chip and ruin them all. I work hard on my amethyst with tile nippers, pressure trimmers, and hammers. It’s a lot of work, but leads to a fine finished product.
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Post by greig on Nov 19, 2020 11:27:59 GMT -5
Whelp, we had a power surge yesterday and the rotary is fried. It was an offbrand lortone, from ages ago that we got from our local lapidary supplier for a total steal price. I think I'm going to purchase a Lortone 33B to replace it. Should speed things along being able to run 2 batches of rock at once to fill the vibe. Definitely appreciate the suggestions, yesterdays clean out looked better than the first. A lot less chatter. Unfortunately the surge fried it a few hours after clean out. So I got to do it twice. Looks like my rock tumbling is on hold for the foreseeable future. FYI - You can replace the motor (a new replacement for about $30 USD). I assume you have troubleshot why it isn't working to confirm the motor is kaput and not something else.
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Prov
starting to spend too much on rocks
Member since March 2020
Posts: 116
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Post by Prov on Nov 24, 2020 13:29:45 GMT -5
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kyoti
has rocks in the head
Member since June 2020
Posts: 542
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Post by kyoti on Nov 25, 2020 9:38:01 GMT -5
Great work! They came out well Prov . It's a tricky material. Lots of good advice in this thread for tumbling it. I have problems like this with my sugar agates. A stern glance could fracture them. I'll to try the sugar trick.
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Post by hummingbirdstones on Nov 25, 2020 10:01:16 GMT -5
They came out great! You did a good job taking some advice and using it to perfect your skills. Beautiful stones.
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Fossilman
Cave Dweller
Member since January 2009
Posts: 20,681
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Post by Fossilman on Nov 25, 2020 10:32:44 GMT -5
I tumble mine with Obsidian.... Some still come out fractured....
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