reynedrop
starting to spend too much on rocks
Member since February 2020
Posts: 204
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Post by reynedrop on Feb 22, 2020 12:36:39 GMT -5
Maybe a stupid question but I’m new to the hobby! Long story short, I bought 26 lbs of raw/rough rocks and minerals, including 1 lb each of peridot and epidote. When they arrived, they were more like clusters in general rock shape with small crystalline formations on the outside, and those formations fracture off very easily. The bags these came in had tiny crystals all over them from transit. Before I knew anything about tumbling, I put two pieces of the peridot in with many other rocks (ranging from chrysocolla and fluorite up to dumortierite and topaz), and I’m not impressed with how this tumbled at all. These photos are of a few pieces of the raw stone that are average for what I recurved, plus the rough tumbled (course grit for 5 days) peridot. My question is basically, are these stones even ones that should be tumbled or could polish well? I’m not necessarily looking for great specimens as these will most likely he used as “Crystal healing” gifts for a friend. If I can tumble them and they will polish, what can I expect from that? I ask primarily because I know the minerals themselves have a hardness of 6.5-7, but I can’t tell what else is in these “clusters” and what kind of hardness they have. Also, is there any possibility of having a nice, even if small, specimen from these types of rocks? How would one go about getting those? These ones are so confusing to me. Thank you!
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Deleted
Deleted Member
Member since January 1970
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Post by Deleted on Feb 22, 2020 13:08:04 GMT -5
My question is basically, are these stones even ones that should be tumbled or could polish well? I’m not necessarily looking for great specimens as these will most likely he used as “Crystal healing” gifts for a friend. If I can tumble them and they will polish, what can I expect from that? I ask primarily because I know the minerals themselves have a hardness of 6.5-7, but I can’t tell what else is in these “clusters” and what kind of hardness they have. Also, is there any possibility of having a nice, even if small, specimen from these types of rocks? How would one go about getting those? Good questions. From your photos, these appear to be clusters of crystals in/on matrix (like the lava bomb peridot from Arizona). The problem with tumbling wouldn't so much be the hardness of epidote or peridot, but that the matrix can be softer and/or that many of the crystals are not tightly bonded to one another or to the matrix. I would think that a lot of this type material would fall apart during tumbling. If there are any crystals large enough to facet or cab, those could be extracted and polished. If tumbling, use lots of cushioning for epidote, as its crystals, while hard enough, are somewhat fragile due to its perfect cleavage. I have also seen sparkling loose smaller crystals of these epoxied onto a backing (either another stone or metal). Another option to try might be to slice a piece into slabs, stabilize with resin, and either cut to shape to show off the druzy surface, or round over and make a traditional cabochon. I personally haven't done either of those, but perhaps someone here has and can offer further advice.
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reynedrop
starting to spend too much on rocks
Member since February 2020
Posts: 204
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Post by reynedrop on Feb 22, 2020 13:32:34 GMT -5
My question is basically, are these stones even ones that should be tumbled or could polish well? I’m not necessarily looking for great specimens as these will most likely he used as “Crystal healing” gifts for a friend. If I can tumble them and they will polish, what can I expect from that? I ask primarily because I know the minerals themselves have a hardness of 6.5-7, but I can’t tell what else is in these “clusters” and what kind of hardness they have. Also, is there any possibility of having a nice, even if small, specimen from these types of rocks? How would one go about getting those? Good questions. From your photos, these appear to be clusters of crystals in/on matrix (like the lava bomb peridot from Arizona). The problem with tumbling wouldn't so much be the hardness of epidote or peridot, but that the matrix can be softer and/or that many of the crystals are not tightly bonded to one another or to the matrix. I would think that a lot of this type material would fall apart during tumbling. If there are any crystals large enough to facet or cab, those could be extracted and polished. If tumbling, use lots of cushioning for epidote, as its crystals, while hard enough, are somewhat fragile due to its perfect cleavage. I have also seen sparkling loose smaller crystals of these epoxied onto a backing (either another stone or metal). Another option to try might be to slice a piece into slabs, stabilize with resin, and either cut to shape to show off the druzy surface, or round over and make a traditional cabochon. I personally haven't done either of those, but perhaps someone here has and can offer further advice. That was what I was thinking re: the matrix, I just didn't know the words for it! The peridot pieces I tumbled seemed to lose quite a bit more volume than the other rocks in the tumble, and given the hardness of the peridot, I definitely thought the surrounding matrix was softer. Looking through my rough, I can't see any crystals that seem larger than a pen tip... which is frustrating but also what I get for what I paid (I think something like $7/lb for these). I don't have any cutting tools right now (currently don't have a good place to do so as we are renting). I like the idea of the slabs but without a "shop" area (we're renting), probably not something to start yet. Perhaps I'll try to tumble a few pieces later just to see how they turn out, maybe when my other tumbler gets in as I don't want to waste time on an experiment like this. I have some plastic pellets, but would ceramic be better?
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Deleted
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Member since January 1970
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Post by Deleted on Feb 22, 2020 15:35:46 GMT -5
The large xtls are definitely rarer, but the smaller, druzy clusters can be attractive if you can manage to get them to hold together. Sounds like you got a good price. You might experiment with stabilizing a piece prior to tumbling using Cyanoacrylate glue (e.g., super glue). Get the thinnest formula you can find (the thicker varieties won't penetrate into fissures). There are very thin versions aimed at lapidary users, but craft stores should carry "super thin"/"ultra thin" formulations. I personally am not a fan of stabilizing, but it may be necessary for crumbly pieces like yours. Make sure the rock is completely dry. Then warm the rock gently immediately before applying the glue (sitting it in a warm place in direct sun will usually do, though you could also place in your oven if it has a "Warm" setting of around 200F) and place on a sheet of wax paper to catch any dribbles (you probably don't want the rock stuck to your table or counter - the thin varieties run like water). Let cure for whatever time recommended on the glue instructions, then tumble. I think plastic pellets would be fine - just want a cushion to help avoid other rocks in your load from chipping at your crystals. Minimal cost to give it a try. You might also check to see whether there are any rockhound or lapidary clubs in your area. Many have workshops with shared equipment and people who will share experiences, help you learn, and/or may be able to suggest alternatives after seeing your pieces in-hand. Look in your local directories, or search online (there are a couple of US nationwide directories here and here).
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reynedrop
starting to spend too much on rocks
Member since February 2020
Posts: 204
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Post by reynedrop on Feb 22, 2020 17:57:13 GMT -5
You might also check to see whether there are any rockhound or lapidary clubs in your area. Many have workshops with shared equipment and people who will share experiences, help you learn, and/or may be able to suggest alternatives after seeing your pieces in-hand. Look in your local directories, or search online (there are a couple of US nationwide directories here and here). You would think/hope with certain well-known mines so close by, we would have a mineral club! I was able to find one with and the dues are very reasonable- thought it does seem to be more geared towards rockhounding and monthly meetings. I don't think they have any lapidary equipment to use, sadly. When we eventually move, the city we will be at for 2.5 years (with any luck anyway) has a rouckhounding club too it seems! Also doesn't look there are any places with their own workshops, but maybe if I get over being so shy I can find people willing to share equipment or mentor me IRL. Thank you
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Post by rmf on Feb 22, 2020 21:21:09 GMT -5
reynedrop epidote, Ca2Al2(Fe3+;Al)(SiO4)(Si2O7)O(OH) is more pale green (typically) peridot (Mg, Fe)2SiO4 what you have looks more like peridot and as has been stated the stuff from volcanic bombs in AZ and NM tends to be relatively small grains that are packed together. If they are pea size they would tumble fine just small. What you have looks like the compacted grains from a basalt vesicle. These are probably too small to tumble. I had to stabilize one with cyanoacrylic glue to keep the specimen from falling apart. Not a good tumbling candidate. When tumbling try to keep similar hardnesses together at least in the fine and polish or they hard stones will damage the softer ones.
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reynedrop
starting to spend too much on rocks
Member since February 2020
Posts: 204
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Post by reynedrop on Feb 22, 2020 22:41:51 GMT -5
When tumbling try to keep similar hardnesses together at least in the fine and polish or they hard stones will damage the softer ones. I figured this one on my own after I destroyed some fluorite If I look closely at what I have, it SEEMS that I can slightly tell the difference between the clusters labeled as Epidote and those labeled Peridot- but I will say that when I first got them, I felt awful that I struggled to determine which was which and decided I would never put them near each other for fear of mixing them up. If they ARE the same, that would explain a lot. It's so hard to see the structure on the crystals (maybe I should get one of those jeweler's magnifying glasses). I guess I could always take some HCl and see if the specimens dissolve Each particularly specimen is about 1/4-1 oz, but clearly the crystalline structures are tiny. I really wanted to do something to overall "smooth" it out (for texture purposes- and because if these go in a velvet bag with tarot cards I worry about the tiny crystals fracturing off), but I'm not opposed to just leaving them raw I guess. I don't think there's anything else I can do with them at this point.
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