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Scarodactyl
Oct 22, 2015




It's been a while since the gems and jewelry megathread died, and I thought it was time to bring it back.
Old thread here: https://forums.somethingawful.com/showthread.php?threadid=3331917

I'm a life-long gem enthusiast--I don't have any gemological credentials but I do have a masters in geology and a fair amount of experience with colored stones (ie, gems that aren't diamonds). I am a coauthor on a few papers in Gems and Gemology too.

I am a jeweler by trade but mostly make offbeat wire wrap stuff so I can't answer in-depth questions about the more traditional side of the jewelry trade. Previously JohnnyRnR was our resident font of knowledge on that topic but he hasn't posted in a while, so we can wing it on that until someone more qualified comes along.

On the lapidary side of things I cut cabochons and am happy to answer any questions about that. Hopefully we can get some of our resident faceters back out of the woodwork too.

I'm also in to gem microscopes and am happy to discuss them and gem micrography in general given any excuse.

Happy to answer any questions I can.

Just to kick things off, here are a few close-up photos of various gems under my 'scope.


Neat little iron oxide inclusions in a Moroccan agate.

Reflective inclusions in sodalite (maybe tiny pyrite cubes?)

Closeup of a bug in "amber" (the amber is probably fake but the bug is real).

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Scarodactyl
Oct 22, 2015




Beautiful work on that stone!

Yes, it is the eternal curse of the lapidarist. There will always be more rough material than there is time to cut it. That will also never stop you from buying more.

I did finally get to some of the moonstone rough I picked up at Tucson this year. None of the Indian dealers I talked to had any top notch rough, I assume that is getting cut in-country since there were plenty of cut stones for sale. Fortunately Madagascar came through for me with some interesting rough that cut up better than I'd expected.

Always a pain to get orientation perfectly right, but worth it in the end.

Scarodactyl
Oct 22, 2015




Nice stones! Chipping an opal at some point is inevitable.
I was at that meeting with a raman spectrometer, for the record. We could scan it at the next meeting if you'd like confirmation. It looks a bit more like ruby in fuschite to me (possibly with kyanite) than ruby in zoisite.

Scarodactyl
Oct 22, 2015




Seluin posted:

If you don’t mind a more pastel shade, you could also maybe find some lighter garnets that are also worth less...just from the other end of the spectrum If you want deep saturated color + brightness and sparkle at most lightings, you’ll likely need to pay more for it.
Garnets are a bit paradoxical on this. In the classic red/pink color range really light tones are fairly rare, so you don't get the same kind of super cheap pale material that you would with beryl or quartz or what have you. Light toned pink and peach garnets in particular are a really hot commodity right now (see how 'Mahenge' garnets have been selling). Nice rhodolites like above have crept up in price too, from what I've seen.

There are so many colors and varieties that span a wide range of prices that there is something for everyone--there is a lot more to garnet than overdark red stones.

Tangentially relevant, this gives me s good excuse to show off my new toy, a dual LED/xenon flashlight.

Great for showing off color change in gems, like this blue to red color change garnet:


https://www.youtube.com/watch?v=LoDTORlPECY

Scarodactyl
Oct 22, 2015




Tsavorite is one of the rare exceptions (and it's sort of in its own world anyway, geologically and price-wise). The light green "merelani mint" garnets can be a great deal that way, though they're still pretty pricey.

Scarodactyl
Oct 22, 2015




Aquamarine can actually range yet deeper in color. Among other locales True North Gems was finding unusually rich blue beryl in the Yukon. All busted up but quite beautiful:

Natural spinel or sapphire in this color range will definitely be more expensive than even very fine aquamarine, carat per carat (unless you mean synthetic).
Topaz is a good alternative--stones in this color range are all treated by pretty heavy irradiation to produce the color, but still a nice gem.
WRT this stone:

I don't think this is aquamarine, and I'm not sure why the GIA put it on the page. It looks like maxixe-type beryl. These stones have a strong steely blue color (or sometimes blue-violet or purple!) coloration which is induced by irradiation, sometimes natural but usually artificial. The color fades with exposure to sunlight, though how quickly varies a lot. It also shows unusually strong dichroism, deep blue to grey/colorless, as they note under the picture.
Aquamarines of good quality in that color range are very desireable and expensive. But more included specimens can sometimes be had more affordably. I have some almost opaque crystal specimens somewhere that are a very deep blue.

Incidentally, there was a recent find of what they're calling "chrome aquamarine" in Nigeria, aquamarine with a bit of chromium mixed in. Chromium induces a rich pure green color in beryl (it's one of the colorants of emeralds), and when you add a pinch of it it to an already intense blue aquamarine it gives you a nice rich cyan:

(Clipped from a video posted by Joshua Hyman [a gem dealer] on Facebook. No doubt prices will be astronomical if you're lucky enough to get in line to buy one!)

Scarodactyl
Oct 22, 2015




Lbl: I'll bring it with (assuming I don't forget). Bring whatever you'd like scanned.


That sapphire is stunning. Australia's blues can be pretty decent but the yellow color range is world class. What an amazing ring!


Just a quick lapidary checkin:

Five Peruvian gem silicas and a moonstone, not too bad for a day's work.
Gem silica (sometimes called 'gem chrysocolla' depending where you live) is a type of chalcedony colored blue to green by copper salts. It is often closely associated with chrysocolla, which is a sort of semi amorphous copper silicate. At its best it is an insanely rich poolwater blue with rich glowing translucency. This is lower grade stuff, with greener color and patterning, but it still makes for a nice gem. I bought a ton of this rough, and you never know how it's going to look inside before it hits the saw.

Scarodactyl
Oct 22, 2015




A lapidary grinder, or just a normal bench grinder repurposed for lapidary work? A nornal bench grinder isn't designed to be safe when used wet as is needed with stone so that isn't recommended.
There are a few good brands of rock specific ones. I use a cabking, though diamond pacific's lineup are probably better in some ways. Either way, diamond pacific nova wheels (their soft diamond impregnated resin wheels) are the best and worth the extra money they cost.
That being said there are quite a few different options depending on what you want to do and your general budget.

Scarodactyl
Oct 22, 2015




The flat grinders (flat laps) do offer a cheaper and more compact option for cutting cabs. Some people prefer it to vertical wheels and almost all of the industrial cutting shops seem to use them. There are some downsides too. You can only have one disc on it at a time so you hVe to switch them as you go to finer grits. It is also a bit harder to get a nice rounded top without flats. On the other hand it is easier to intentionally put on flats.
One popular flat lap is the 'all u need', which I think runs about 500 dollars new with some cutting discs. You can probably find something cheaper used. There are some good groups on facebook like 'lapidary equipment marketplace' that make it easier to find good used stuff as well.
If there is a rock club in your area they may have equipment of their own that you can try out before buying anything.

Scarodactyl
Oct 22, 2015




Faceting requires quite a bit of preciaion. Since the angles have to be repeatable to hit the same planes with subsequent polishing laps. It's possible to get a faceting setup and jury rig it onto a flat lap, but it is typically a fristrating exercise. Doubly so with some of the cheap no name setups. Some of those are apparently totally unworkable from the start. Ypu'd do better to save just a bit more and get something like a used raytech shaw faceting machine to dip your toes in for faceting.

Scarodactyl
Oct 22, 2015




Thst's interesting. Garnets will never fade, and red glass shouldn't either. Could you post some pictures?

Scarodactyl
Oct 22, 2015




Garnets can color shift, from purple/magenta under LED to pure red under incandescent. Others can shift from bronzey brown under cfl to pink/red under other lighting. This looks like it is in garnet's normal color range anyway, can't identify it for sure from a photo unfortunately.

Scarodactyl
Oct 22, 2015




Nice stuff, Leperflesh!
Let's start with the foredom. That's a flex shaft rotary tool, and Foredom is the top brand in that field. It seems that all the third party flex shafts are made to be compatible with them. So that's a real gem right there. In lapidary it's used mostly for carving stones (which could be full carving, freeform shapes or following the three-dimensional contours of a stone like fire agate that has irregular layers of color). Also very good for shaping opals to follow bars of color if you want really high yields and don't mind a more irregular shape. It probably takes 3/32 inch bits, though, rather than 1/8 like a dremel (at least the quick-change handpiece I got for my foredom clone does).

The hi-tech is definitely much like an all-u-need, which is a capable tool for starting out on. I use a setup with vertical wheels (you grind on the edges rather than the top) but both styles have fans and proponents. You can also mount a saw blade on one of these. One nice feature of sintered diamond tools is that they're a lot better at grinding hard things than soft things (unless there is a serrated edge or whatever) so they will tend not to wreck your finger if you nudge them, NOT that I recommend it. It looks like it should be perfectly compatible with any normal lap you buy.
As a side-note, cutting opal has some upsides. It's soft enough it grinds relatively fast, and you can use a chemical polishing agent for a quick and painless polish. Cerium oxide works great, though tin oxide is recommended as well. These polishes actually have a chemical interaction with the surface of silicates and silicate-bearing glasses/amorphous silicate like opal and the water they're mixed with, and produce a much finer and easier polish than working with finer and finer diamond grit will give you. You can often go from 1200 grit or so to a final mirror polish. Opal is heat sensitive in addition to other things so don't let it get hot, use enough water to keep it cool.

For dopping I use superglue gel and just let it set for a few hours or overnight. Wax is faster but a huge pain to work with. Any old section of dowel will do for a stick as long as you can cut the end mostly perpendicular (this does not apply to faceting, of course, but cutting cabs is loosey goosey and a lot more forgiving).

I think you are right, the chisel thingy is likely for splitting rough. Sometimes people will boil and freeze stones beforehand to loosen them up, since you want them to split along natural fractures. There are times this is appropriate but that'd be more for faceting than cabbing.


Claes: nice! It'll be interesting to see its performance when it's done. Dark blue C with a teal cross-axis?

Scarodactyl
Oct 22, 2015




Freehand cabbing is done quite a bit and probably just fine, if you don't mind short fingernails and the occasional scrape while you learn. I much prefer a dop. For removing CA I usually grab the wooden dowel right below the stone and squeeze to flex it and break the bond, then peel some ofd with a box opener, then grind the back down to clean up scratches and remove the rest of the glue.

I have never used a horizontal saw setup but people do it. I am not sure if stones are fed in by hand or what. I use a ring saw to trim and slab small stones and I just feed them in by hand, because the blade tends to just scrape skin a bit if you were to touch it, but that's a normal vertical saw setup. That one is used with water only, which I prefer a lot because I like to slice opals and turquoise and other stones which can absorb oil. You can also use a cheap wet cutting tile saw for this if you buy diamond blades for it.

Cross contamination is mostly an issue with diamond grits used for grinding. Each lap has a designated grit, and it will not tend to grind off pieces of the stone bigger than that grit* so you can use it from stone to stone as long as you don't get the coarser grinding grit onto the finer laps. Cerium would be on your final polishing lap, so you definitely don't want any coarser grit to get on there. So basically keep your different grit laps separate but you don't need to worry about using them on opal and on other random rocks.
That said, this is much more forgiving when cutting cabs than in faceting.

Thunder eggs are similar to geodes but form in pointy-edged cavities in rhyolites rather than in sedimentary layers like geodes do. They can have a variety of cool things inside.

*sometimes some stones (some garnets in particular) will chip off bigger sharp bits just to screw with you, and those can be a real nuisance, but it isn't that typical.

Scarodactyl
Oct 22, 2015




Even if it came out dark I'd like to see it. You can always have a maglite right out of the field of view, works for selling dark tourmaline rough.

Scarodactyl
Oct 22, 2015




There isn't really a set price for these types of things, though you can find good comps by searching arpund eBay and online shops to get an idea what it would cost to replace. I think you paid a very reasonable price.

Scarodactyl
Oct 22, 2015




Inclusions aren't desirable in emerald (aside from trapiches but that's a different can of worms). They are considered particularly acceptable in emerald because clean stones are very rare (apparently chromium tends to mess with their crystal growth), but stones that are properly clean sell for far, far more.

Scarodactyl
Oct 22, 2015




Beautiful work! Ruby or spinel?

(One hell of a girdle though!)

Scarodactyl
Oct 22, 2015




Heat resistance varies quite a bit from stone to stone. Sapphires are fine up to around 2000c (though these temperatures can certainly affect them, hence heat treatment), but beryl (which emerald is a variety of) will turn to opaque white ash around...I think 800ish c? I've done it once, it wasn't pretty.
For a specimen like this, though, you're not dealing with a single crystal, but a specimen composed of many intergrown crystals of different minerals. They will have different heat tolerances and different rates of thermal expansion. They're also much harder to clean, impossible in many cases to get soot out of fine crennelations, vs a single crystal or faceted stone.

So yeah, a fire could totally destroy a specimen like that with ease. That said, their valuation is insane even by massively-inflated-valuation standards, and I think it's fair to disbelieve anything they say.

Scarodactyl
Oct 22, 2015




Yeah, for faceting it's usually best to find someone local who has a machine who can run you through some stuff because the setup cost for equipment is pretty high, so you want to be able to try it before you sink potentially thousands into a machine and laps. That book has a great reputation. For a quick overview there is also Arya Arhkaven's Faceting 101 series on youtube: https://www.youtube.com/watch?v=oD6ZlNmtwmM

Cutting cabochons is a lot easier and less technical, though it does take some practice.

Gemological education is going to vary in usefulness depending on what you want to do, I think. I've been considering it myself since I'm at a point where I'm doing a bit more stone sorting (specifically separating treated from untreated from synthetic, baseline ID is easy with a raman), plus having some sort of gemological credentials is always handy for establishing cred. But it isn't essential if lapidary stuff is your main goal, and an awful lot can be learned on your own--for instance the GIA has all of their issues of Gems and Gemology available for free download, which is a ton of high quality and easy-to-read research at your fingertips.

Scarodactyl
Oct 22, 2015




Oh yeah. This is a pretty typical cut, kind of a shallow emerald. If Johnny doesn't have one on hand I might be able to find one at Tucson towards the end of this month if you can get measurements.

Scarodactyl
Oct 22, 2015




It is probably pieces of quartz bonded together with metal leaf mixed with epoxy (broadly imitating natural native gold in quartz veins). This is most typically done with faux-turquoise to give it a spiderwebby look (or with purple faux-turquoise which is a weirdly popular item).

Scarodactyl
Oct 22, 2015




Is anyone else at the Tucson gem shows? It might be fun to do another meetup if so.

Scarodactyl
Oct 22, 2015




https://www.gia.edu/limited-time-offer-enroll-GIA-essentials-elearning-courses-no-charge
The GIA is offering their three intro courses (normally 250 bucks each) for free. If you do all three you get a credential of some sort, no idea if anyone cares (I would think Graduate Gemologist is the one that really matters) but still it is something! I signed up for all three, I will report back.

Scarodactyl
Oct 22, 2015




That came out great!

Scarodactyl
Oct 22, 2015




Solenna posted:

After doing a bunch of wire weave bracelets I got into making wire wrapped jewelry, and I would like more semi-precious rocks to put a bunch of wire around. I'm a little (very) hesitant to just buy a whole bunch of cabochons from random Ebay/Etsy sellers so I figured I'd ask here. Does anyone knows a decent website for stuff like tiger's eye, quartz and labradorite cabochons? Or specific sellers on Ebay or Etsy.

One of the pendants I made:


That's nice work!
If you're looking for good bulk type stuff a friend of mine runs http://wholesalerocks.biz --he's good at sourcing quality stuff and his prices are very competitive.
If you want something more specific/artistic another friend's etsy page is https://lennysrockshop.etsy.com --he's an exceptional cabochon cutter with an eye for composition.

Scarodactyl
Oct 22, 2015




Nics pics! (To be a bit pedantic they are technically photomicrographs--microphotographs are photos made tiny. Apparently they got there first, namingwise).

For prep alochol with fresh qtips works pretty well though it's kind of slow and a pain. Maybe an ultrasonic cleaner for something stubborn. One issue is some gems are triboelectric, so when you rub them they develop static electricity which attracts more dust.

Steady hands aren't needed with photomicrography since the camera is fixed in place and remotely triggered.

Scarodactyl
Oct 22, 2015




Yeah, your average jeweler is usually dealing with the best sellers and likely doesn't have great contacts for sourcing more unusual stuff. Do you have an idea of general budget and diameter needed?

Scarodactyl
Oct 22, 2015




Yeah, feldspars love cerium and will polish to a mirror finish with it even with a relatively 1200 grit prepolish. It will even smooth out the dome on a cabochon to a limited extent. Cerium does have to be used wet because it is a chemical polish and the water is essential to that.
Caveat: polishing a large flat surface is more difficult than a dome. People have luck with polishing pads used on granite slabs, but if you use one be sure to wear a respirator. Silicate grit can be quite nasty in the lungs.

Scarodactyl
Oct 22, 2015




In America there are a ton of resources for rockhounding by state, but as I understand it it is harder in Europe. Looking arpund on Mindat can give an idea of deppsits in your area, though what's accessible (especially legally) is harder to assess from that. Germany does have a few noted gem deposits, including the old time yellow topaz deposit in Schneckenstein (now very closed) and blue hauyne. Plus the old tymie agates of Idar Oberstein and all the gem stuff in that area, though I remember it being a bit of a tourist trap when I went as a kid.

Scarodactyl
Oct 22, 2015




Mmm, that's quite an impressive lineup! How much Laurenthomasite was even produced? I can't imagine there was much to go around, though I have not yet read up on it.

Scarodactyl
Oct 22, 2015




I just got my very first opposed bar back from the cutter!


Light pinkish purple Nigerian amethyst. Couldn't be happier with this.

Scarodactyl
Oct 22, 2015




Just over 93 carats. It was cit for me by Eric Bardawil who is something of a rising star I think. He's done a couple amazing cuts for me, and I just sent him the four best from a parcel of topaz I got in from Nigeria.

A bit rare to find natural greens and yellows, or blues this rich for that matter (though thr cell phone camera exaggerates a bit). I'll post those when they're done.

I just love Nigerian topaz. The peachses may fade with sunlight, but the blues and yellows are 100% stable.

Scarodactyl
Oct 22, 2015




'Little' is awfully relative. It's quite well sized for a red beryl! Wonderful color too, great find!

Scarodactyl
Oct 22, 2015




Scarodactyl posted:

Just over 93 carats. It was cit for me by Eric Bardawil who is something of a rising star I think. He's done a couple amazing cuts for me, and I just sent him the four best from a parcel of topaz I got in from Nigeria.

A bit rare to find natural greens and yellows, or blues this rich for that matter (though thr cell phone camera exaggerates a bit). I'll post those when they're done.
And here they are! Alas, the yellow sold quickly after Eric posted a video on facebook so I never got to see it in person, but the blue and greens came out amazing.

Greens are super rare in topaz, so having two is pretty exciting. Better pics in a bit.

Scarodactyl
Oct 22, 2015




For slicing up stones I use a ring saw by Gemini. It's a super cool saw where the blade has no center, just a rim and is driven from below by a belt. This reduces drag, allows finer control of curves and has much more cutting height per saw diameter than one that has to have a hub in the center. Plus it's water cooled so no worries on cutting turquoise or opals. I don't know if that's at all applicable for your situation but it's the saw I know and like.

Scarodactyl
Oct 22, 2015




For slapping a blade onto another saw (a tile saw is usually the classic starter choice) I'd just get a generic smooth-edged diamond blade. Make sure there's enough coolant so the diamonds don't come out and the antler doesn't burn.

Scarodactyl
Oct 22, 2015




Some quartz is just like that. What kind is it?

Scarodactyl
Oct 22, 2015




Xun posted:

It's a random piece of synthetic "sky blue" quartz I got that actually looks just white in person. My 1200 lap scratches the poo poo out of it and tbh its pretty scratchy on harder stones too. Sometimes the facets barely look better than my 600 lap, I thought it just wasn't broken in but I've used it on multiple stones at this point and it still sucks
Ever hear of 'shitrine'? It's a particular batch if synthetic citrine that went around the market for a bit which was famous for being almost impossible to polish. You could identify it because heating it turned it blue (due to cobalt doping for...some reason?)
Point is some quartz, and especially some synthetic quartz, is just that way inherently.
Your time is really too valuable to fight with uncooperative material anyway. Or with synthetic quartz in general. If you want to do some quartz richly colored natural amethyst is still inexpensive but the end result with precision cutting has a great multiplier on value. Or if you want something weirder, some nice lavender quartz with that opalescent translucency also rarely fails to hit.

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Scarodactyl
Oct 22, 2015




Rutilated quartz is amazing stuff.

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