How to Cut Gemstones | Tips for Dealing With Inclusions & Heating

Hi, I'm Steve Moriarity from Moriarity's Gem Art. We're a jeweler on the Square and Crown Point, and we're also available online at moregems.com and tanzanitejewelrydesigns.com. So today what we're going to talk about is this beast. This I've been putting off cutting for about six months now, and it's time to get to it. You know, the reasons that have held me back on this is because of the difficulties of the inclusions that are in it to deal with, and also a little bit of fear because I've seen a piece like this before and actually it fractured on me while I was cutting, and it was going to cut a hundred carat stone. This one will probably cut a 30 and a second stone on this side that's probably going to be somewhere around 10 carat. So over the next week or so we're going to run through the process of cutting this and show you cutters the difficulties that I have to deal with, and hopefully we'll end up with a couple of beautiful stones. This is a natural color tanzanite. This is how it was mine. It has very pure colors, no green to it, not an extremely dark color, but really a nice crystal. And I'm going to show you what the dichroic colors or trichroic colors in a natural tanzanite look like. So let me see if I get this right. How's that look? So this should be the purple and yellow, and that may be the blue and yellow, and this direction is maybe the blue and the purple. I can't see it so I'm just doing it from memory. So the yellow color that you see in there, what's going to happen is once I've cut this stone and get all the inclusions out, because inclusions tend to break once you start heating these, because we're going to heat this to a thousand degrees and that yellow is going to disappear and just leave the blue and purple, and that's what we expect from tanzanite. That yellow is kind of making this look like diesel. They call this diesel. It's kind of a brownish, reddish color. And once it's heated, that's going to disappear and we should have a couple of beautiful tanzanites. This is our crystal. Very, very clear crystal, so I don't really have to use immersion fluids if I had an issue that the surface was rough and I couldn't see into it easily. You can use wintergreen oil. This is available online. It's just pure wintergreen oil. It's got a refractive index, maybe 152. So on most gems it's very helpful. You can either just wipe it on the surface or you can immerse it and look into the gem. So you can use a light or you can use your flashlight. Now I've looked at this in the scope and used the visor and I've tried to plot out a map showing where all my inclusions are so I can try and figure out what to cut from this. We've got issues of the way this crystal is shaped on the back. The angle that it's at we have to consider. So let's take a look at the map I've made of this stone. I've plotted out all the inclusions and the different sizes. So first of all, there's a lot of inclusions up here at the top. So I've X'd them out. That's unusable material. I'll show you that. So those inclusions are up in here. They're in both tips of both these crystals. So we're just gonna cut that away. And the next inclusion that's a problem runs right across here. So it's 5.5 millimeters from the edge and I've got about 20 millimeters height and we've got about 30 millimeters across this way. So my usable depth on this is 12 millimeters. The actual depth at this point is 14.7 millimeters. So let me show you that. So this is the inclusion that I've got to deal with. You know, I've estimated its depth. These often run deeper than you expect. So you assume if you think it's two millimeters deep, it's two and a half, three millimeters. You'll find that through all your cutting that everything is deeper than what you think. But I've tried to estimate it well. And the other issue, because it's a twin crystal, there's usually a plane that runs through here and in some pieces you can see absolutely that there's a visual plane. In this piece you can't see it, but I'm going to assume it is and that we're not going to cut across that plane and I'll show you that in another picture. So this is between the two crystals and you can see this plane that runs here. I'm not sure, I think this is the plane we're going to deal with and and we're going to saw it right across that right through here and we're going to cut a stone here So this is the plane we're going to saw through next. This is the inclusion I have to deal with. I have determined that this inclusion side is going to be my pavilion and I look at this point being where the culet will be. So I do some kind of brilliant cut. The cut is naturally going to go above this inclusion if I predicted the depth correctly. Now we're going to saw the crystal across that line that separates the twin crystals and then we'll determine what we're going to cut. So I've got this little point here that's kind of in the way of getting a straight cut down the crystal. So I'm going to try and cut into that Okay, hit it. All right, so I got rid of that little crystal tip. Now I should be able to hit this line again. You can maybe see the line I'm going to cut down. As I was cutting it split right along that line so there was a weak point there. So but it split perfectly for me so I didn't even have to saw it off. So that means that during cutting it probably would have split there if I tried to cut it across that crystal. I cut maybe a third of the way down and then it just split along that line and it's exactly the line that showed that came out the bottom of the stone. So there is another line over here so I hope it's not an issue with that but we'll find out when we start cutting this bigger piece. So we've got our two pieces now we'll dop them up and I'll cut away the bad parts of it see what I've got left and determine just what kind I'm going to do with these two pieces. So before I dop this up I'm going to take out the problems that are in the tip and work on the shape a little bit so just it makes it easier to figure out what the center of the stone is when you're dopping. So this lap I believe is probably about a 400 I'm not using very coarse right now and I'm just going across the dop to try and more evenly use across the lap more evenly use the diamond that's in it and that's got most everything out of this crystal. Now I'll more easily find the center when I'm dopping it and then the same with this one the inclusions go a little further in this this piece. All right here's our finished preforms they're both looking kind of square cushiony to me. So this started out as 112 carat currently we're about 101 carats here's this is a 66 carat piece now this piece measures 18 by 18 by 14. Now I if you want to figure out the percentage depth that is you take the depth and divide it by the width and that gives us 77 percent on this stone and 77 percent is is a deep enough material that you can cut it properly. The other piece this weighs 35 carat it measures 15 by 15 by 11 and if we divide 11 by 15 we get 73 percent so this can be somewhere between 73 and 80 percent depth so I say it's looking like some kind of cushion. I do have this issue here that I'm going to have to match all the way around it but looking at this I'm estimating maybe 40 percent out of these pieces of rough possibly 45 but probably 40 percent so we're going to get somewhere between 12 and 15 carat out of this piece and maybe 25 to 30 carat out of this piece. So next we're going to dot this up and get ready for cutting. So I'm going to first dot this larger piece of tanzanite the 66 carat piece and I want to cut the pavilion first so I'm going to dot the opposite side of the side with the big crack in it and first of all I use some dental wax that's available from any drugstore nice and sticky and will form to the stone and hold it in place once you get it centered to where you want it and I'm using a dop that's about the size of the stone I have to use as a centering device make sure there's no flats on it because often we'll be cutting and we'll cut into the dop so pick one that's nice and round and it's a very helpful device in centering your stone. So now that I think I have it centered just press it into the the wax now I'm going to find a right dop that's appropriate size to glue the stone up and then I'm also going to follow through and check my measurement with a millimeter gauge just to make sure I'm accurate. So I'm ready to mix some glue and dot this up it's often best if you dot under the dop but it's also harder to get off and my greatest fear is that this piece of material is like one that broke on me when I was trying to keep this dop loose so I started just putting glue around the edge and then I can peel it off and easily remove it and that's what I'm going to do with this stone just because this stone reminds me so much of that one that blew up on me then I'm going to try and not put too much heat to this even though I have to heat it to a thousand degrees later I'm going to just dop around the edge like I say in in most stones if they will take the heat and you know they're not real heat sensitive you should dop beneath the dop it will hold better you won't have the problem of falling off but this time I'm just going to put it around the edge now I've previously cleaned the stone and the dop with alcohol and made sure all the old old epoxy was off it so we're just going to mix equal parts of this epoxy it's a big stone so we need to have plenty of glue that should be good so what I'm going to do is put the glue up further on the dop and let it just drip down onto it and then it won't get under the stone I say the risk of this is that it breaks free because you don't have that extra support beneath between the dop directly and the stone but I'll be able to just pick this off and have less risk of causing damage from heating up the dop too much and actually causing a problem with the stone I say it seldom happens but it happened on a tanzanite just like this so just manipulate it so you don't get the glue over the edge of the stone you don't want to be cutting into glue it's tough on the lap and it takes a long time to cut through glue so this will need to set ideally overnight but at least three or four hours before you go cutting so it's been about seven hours and we should be good and hard and hopefully it'll stay on the dop for me so let's take it out of the transfer block make sure everything's good and tight usually square it up and now I'm going to try and get it square if you look at it closely you can see I've got a pretty big corner here that I have to deal with so one way or another it's going to have to be matched up on all four sides so first I'm going to cut it 90 degrees and get the four sides square and I'm cutting with a lap that's about a 400 grit kind of check see how square I am and it's pretty well centered so I got the dop in the center of the piece pretty well so now we're fairly well squared up I still have this issue and it's the girdles not all the way over here but we're not going to cut a square we're cutting a cushion shape so there'll be some angles that'll that'll take this material and give me a even girdle all the way over so I've run into a bit of an issue here and on this corner here you can see where that line is and it appears to run a little deeper than I expected so what I'm going to do first is seeing as I know I'm going to have to get rid of this amount of material at least on this side and I can cut that and I know I'm not going to be losing anything I'm going to cut there and see what's left of that inclusion when I'm done and it is possible I may have to change the cut style I'm doing I can see it could be a shield if this is a problem that it runs too deep so I'm going to cut a little bit on this facet that is got me out of square a little bit but I'm going to cut the matching facet to the other side and see what that inclusion looks like so this is the part of the stone that's like a facet on the that's got me on a square that is material I had to deal with but I can cut on this side and take the equivalent amount of material and see what's left of that inclusion before I proceed so it does go a little deeper than I thought I'm not sure if it's above my girdle that I may miss it but it's looked like it could be a problem so I'm going to try and analyze this a little more and I'll get back with you with what I decide to do so this is something that sometimes happens inclusions that you know are there but you don't know exactly how deep they run and looking at this it runs deeper than I thought so making this a square cushion is probably not going to be possible so what I'm going to do I'm going to cut a little more through this inclusion try and get most of it out and then because I won't be square on the top now I'm going to have to remove this stone and redop it to the center so it's going to create a few more problems because that inclusion I'm trying to miss that's up here is going to get closer to the culotte to the center so it's going to create a little more problem so this is why I put this stone off for so long because I knew it was going to be trouble but I think we'll get through it and it's just going to create a little more work so I continue to run into issues with this stone I've gotten most of the one problem inclusion out and I'm now down to 56 carats and you know this is where this wintergreen oil comes in handy because this roughened surface from the cutting lap now when we put the oil on it you can easily see into the stone through that rough surface so the problem I was cutting out is right here but can you see it but if we look further there's a plane that runs across this direction and I'm not going to be able to get that completely out it almost looks like a cleavage plane hopefully it doesn't part there but it is vertical it'll be vertical to my table it'll be out at the girdle of the stone so it's probably not going to show up as long as it stays in one piece and I'll get most of it out but there'll be still a little bit of that left I also spotted a little crystal in here that I hope cuts out because they don't heat well so this is a disaster waiting to happen but we'll hope we'll get through it I'm going to redot this up we're now going to be cutting a cushion that's not square but still hopefully will be a beautiful stone okay so I'm redot once again and I'm going to work at putting a shape in that's going to hopefully remove most of the inclusion that's left I have a little piece here that once I put three facets down the down the sides or five whichever I decide it's going to remove that and and so I'm going to work at forming a nice girdle and hopefully getting rid of most of the inclusion so probably a little bit left of the cleavage plane but like I say it's going to be right out at the girdle of the stone and it's probably not going to show up so I finished cutting this tanzanite using the Nubon 325 which is pretty much comparable to like a 3000 metal disc so I'm going to polish directly from that and to do that I'm going to use a bat lap so and the bat lap is a tin alloy lap that is harder than my tin lap and produces a nice flat facet we use WD-40 to clean it off and then we get your finger a little greasy some diamond this is 50,000 diamond and we spread it across the lap evenly and now you're ready to start polishing I generally run middle speeds on this anywhere from slow to fairly high speed so I'm going to start with the I've got three rows of step facets at 60 degrees 51 degrees and 41 degrees and I'm going to start at the 60 degree because I've got a little bit of inclusion I want to get out so I'm going to polish until I remove it now up to while cutting I use a visor. A visor is much quicker to use than using a loop but once you start polishing you're going to need to move to the loop so you can see much closer so I'm making minor adjustments trying to get back to where I'm polishing the entire facet and this has got just a teeny bit of my imperfection left so I'm going to polish a little bit deeper you don't want to have to polish too far because you're going to have to do that to all the other facets and if you have to go too far you may as well go around and recut rather than trying to polish something out this particular inclusion is very small and it does break the surface so it shouldn't cause any issues with heating smooth no dots for the next facet. I've finished cutting the pavilion now I've got three rows of step facets that are at 41 51 and 60 degrees and now we're gonna take it from the machine and we're gonna transfer it into a v-dot we'll start cutting the crown after glue dries so it's time to remove our dot from the crown side of the tanzanite and this is where I've had problems before but we I didn't put glue underneath the dot but because of the way it formed to the top of the stone there will be some glue underneath it so I will have to heat the dot so this shouldn't be an issue but as I've said before it's been an this you do have to be careful when you're doing this you know I want to get as much off as I can but when you're popping it out you can pop little chips off your stone so just be cautious and then once most of it's off I try and go around the edge of the dot quickly and just get us through as much of that as possible sometimes it'll pop off but I think in this area I've got glue underneath it so we're gonna have to heat the dot and just put the dot over the flame hold the stone tightly putting pressure on the stone and sometimes it pops off that easily but try and hold on to the stone so we're freed and ready to cut the crown of the stone now that we've freed up the crown side of the stone as I tell my cutters the first thing you have to go after is the problems and this stone has a problem the angle here is going to determine what the angle that we're going to cut the girdle at and to do that I usually put it down on the lap try and get a light and appropriate position find out where that's at and try and visually see what's flat not too easy to do and after that we'll cut a little bit and see just where we're at this is set at 46 degrees which is pretty low for for the cut angle but that's what we have to work with still cutting through the glue that was there set it up a little bit higher like to get as much height to this first facet as possible because lower we cut it we cut away a lot of the material that's on the rest of the stone this is the low point that we have to deal with the rest of the stone there's plenty of material and we'd like to keep as much of that as possible by getting this angle up as high as possible so it looks like 55 degrees is about where we're going to be which is good that's a good starting point so we'll probably do something like 55 40 30 or 35 for the three facets I'm going to do a step cut crown so that's formed our girdle 55 degrees finish the step facets around at that 55 degrees and then go on to the next raw facets start cutting the girdle you want to close look at the facet and try and determine whether it's completely square so as you go around higher girdle if this isn't completely rectangular and parallel sides what's going to happen is when you get around this facet the try and make it as square as possible and if it doesn't so this is an issue you're going to run so your options are we cut all the fat in this case I don't have a lot of girdle left to do that or you can feather them in on this facet to the next facet and closer but not as close as possible so normally uh this should be at zero we normally start the lowest facet and set the gauge to zero but because we started at the problem and it was on the end which is actually the highest point and I use zero there once I get around to the thinner edge of the stone my gauge is going to be under zero so it's not a problem because we're well above critical angle and when you go to polish just remember where you started and if you remember that in this case I was on the end that I set to zero so if you start polishing on the end and set it to inclusions were definitely a problem I'd hoped for 30 carat but maybe we're in the 20 carat range that's a fairly deep step cut so I'm hoping tomorrow to take it out of the jar and we hit at least 20 carat and I could still make some money so take it out of the machine and put it in the jar of a tack and by tomorrow should be free we'll weigh it up and get ready for heating and then we'll move on to the next half of the stone and this stone I've decided to cut it down the blue axis it's going to be a deep stone some people may not like it because of the depth but it needs a lot of help color wise this half of the crystal didn't have a lot of color so I'm going to cut it right on the blue and you know hope to get a 10 carat stone it will be a little overly deep but we can design a pendant for it Christopher Michael designed something and and build it in such a way you can't see the depth but that extra depth is going to add to the color of the stone and because we cut it in a stepped emerald cut it should also add to the the depth of well it's time to put our stones in the oven and tomorrow we'll find out whether it's a bad day or a good day because here's our stones we have a 16 carat and a 21 carat now the 21 carat has a little very teeny crystalline inclusion down near the uh cuvette of the stone and crystalline inclusions can be issues they can cause fracturing so what I'm going to do I'm going to heat very slowly I'm going to take 24 hours to go up to 1050 degrees and hopefully the slow rate will prevent the expansion of that crystal to create a fracture in the stone so I'm going to put them in my vessel and cover them with investment this is to slow the process of heating so cover it up and into the oven it goes so this is going to take about 24 hours to finish this process usually I do it in about 10 hours but hopefully it will be successful and won't have an issue tomorrow so the oven is set and started it looks like 24 hours and 15 minutes before I can open that oven back up so we've removed our stones from the oven they've been in for 24 hours about twice what I normally do but it's all because of my fear of this stone cracking it has a few issues inside of one of them and as I've noted all the way along this video I've been a little nervous about this particular piece so we heated it slow over 24 hours and it cooled over the last 12 hours and so now it's time to see what we've got the risks here are the one stone that's included that I'm worried about weighs 21 carats even at $400 a carat we're looking at an $8,000 stone so that's the risk at the moment all right let's see what we've got 16 carat lighter color as I expected look like the new issues light salon color attractive stone no looks clean success purple color not the most intense color but beautiful stone good brilliance and what a relief no cracks so we got a 21 carat that's a little more purple a little deeper color and a 16 carat so 37 carat total weight out of our 112 carat antonite rock and no cracks and just a very attractive stone so I would put these that maybe this one 400 or 50 a carat and this one someone 300 a carat price