How to cut Gemstones: 2 Preforming & Dopping

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hi I’m Steve Moriarty from Moriarty’s Gem Art ( and welcome back to part two of how to cut color gems today we’re going to
show you the material that we’re going to cut during these lessons on cutting
and what I have our piece of citrine in from Uruguay kind of flat get a regular
shape and a piece of garnet and this comes from Tanzania it’s a beautiful
color now fairly big style in the notes should cut a 10 carat size down so what
we’ve got planned for these because these two stones use the two different
types of polishing that I do this will be polished on the bat lab and this will
be polished using the spectra laps and cerium oxide so once you have your piece
of rough the first thing you have to determine is are there any inclusions in
it that will cause problems during cutting so I always use the refract all
this material has a refractive index very similar to quartz so when you put
quartz in here the surface is going to pretty much disappear and you’ll see
everything that’s in as far as the garnet goes the garnet has much higher
refractive index it’s still very helpful to see into it but there’s other
materials like methylene iodide that has a much higher refractive index but the
problem with it it’s very expensive and somewhat caustic and bad to breathe
so the refract all is real helpful on the scene inside stones and I recommend
that you use it on every stone you do so a couple ways of doing it I mean if you
if you look at the citrine in there I mean the surface of the stone is pretty
much disappeared it looks like a piece of jelly within the fluid
and that’s because the refractive index or how it bends light is almost exactly
the same so you can pretty much look into it see where the inclusions are and
then you have to try and work around these you can leave some inclusions in
depending on where they’re at and then the shape of them or how they’re
oriented and sometimes it’s difficult to see but it’s always best to cut a nice
clean stone which I think this one will cut completely clean so two ways of
using refract all you can use it in a glass jar like this or you can just
pretty much coat the stone and even out of the jar it’s fairly easy to see
inside this down you can either use a light like this or you can use a
flashlights very helpful in identifying the inclusions so now when we do the garnet you’ll see
it’s a little more difficult to see into because the refractive index is quite a
bit different this being one five seven on this garnet somewhere around one
point seven four but still helpful no you can you can still see you into the
gem better than you can without it and again you can just coat the stone and
it’s still quite helpful and seeing into the stone and this is another piece
that’s very clean which makes it a lot easier to determine what to cut from you
know have to worry about working around inclusions you know I also recommend in
general using a visor visor is going to help that extra magnification makes it
much easier to see into the stone looking at this piece of rough I’ve
determined I’m going to cut a round brilliant out of it it’s fairly shallow
it’s nine millimeters deep and currently it’s about
Oh sixteen millimeters round in a round brilliant I can expect maybe I’ll need
about 70% depth in relation to width so 70 times 13 is somewhere around 9
millimeters so with luck I’ll get about a 13 millimeter maybe down a 12
millimeter out of this stone because of his shell with depth we’ve determined
that it is a clean stone so I don’t have to worry about any inclusions I look for
the shallowest part of the stone which is over here which this material is not
going to be very useful so I’m going to start preforming by cutting at the
finish point because I’ve got to make it thicker it’s got to be a girdle there’s
gonna be some ground above it there’s got to be Pavillion below it so I’ll
start cutting water running you know the key is getting rid of what
you know you can’t use so as you’re preforming you you get rid of the
material that you know is useless whether it’s because of inclusions or
it’s too thin and then ultimately you can decide what you’re really going to
cut off is down which often changes so on this side I’ve pretty much probably
close to where the girdle will be so I can start working on the other parts
there’s a little point here and around I sure not going to need a point the side
is thick enough I don’t have to worry too much about it I’m getting closer to round so this is a
180 lap I’m working on the bigger the stone the more material you have to work
with the coarser the lap that you use so I’ve got a point down here that’s gonna
straight up and down I can cut it it’s gonna be much closer to round and I’m currently a 15 millimeters I
know I have another two millimeters that I can cut away risking losing material
because I know my debt showing 12 millimeter stone so now I can you know
have to cut it all the way down now I do have to make a position for the table
and where I’m going to adopt the stone because I always cut pavilion first cause you have to do is cut to the point
that the center where the tables going to be as flat where you can adopt the
stone right now I’ve got a little bitty crack
that’s right there that needs to go away and it probably ends right where this
Vivat comes out so it’s pretty much gone and i pretty much have an area for the
table in the center so now if i measure to the center of the stone I’m still
just under nine millimeter in this direction I’m still
over 15 sighs I’ve got quite a bit of material to cut away Shh and you don’t
get rid of it all you can do process I generally just get closed trying to make
a good and round when I shop it’s easier to find the center point so now I’ve got
a pretty round stone I’ve got at least area all the way around the stone except
right there that that will be girdle so the this is probably good enough for a
preform like so here’s our second style this is run like garnet from Tanzania
this one weighs 26 carats and so the first thing I do is in determining cut
is try and take its measurements this is about 14 by a little over 10 millimeters
depth and it’s close to 80% depth and that depth kind of determines what you
can cut out of it this is fairly deep so we can do a lot of different styles of
cutting whether it be stepped or some types of brilliance berry and this is
pretty much like a square cushion so it’s still to be determined what I’m
going to cut out of it but I’ll get rid of a little bit of the excess material
which it’s pretty close to a preform now and again you don’t have to prepare my
it is really an assist when you go to top the donor
and get get the the top in the center of the stone so the closer it is visually
to what you’re going to end up with the easier it’s going to be to get a
position correctly and really this is probably good enough the stone could be
round could be cushion but I think we’re going to do a cushion out of this okay
here’s by two rough reforms and now we’re going to DAP these out in
preparation for cutting so there’s a few techniques I use one one is to use a
millimeter gauge this one has nice sharp points on it so it does actually draw
good lines so if you go beyond oh you go about 3/4 of the way across and then you
make a line and then go the other side make another line and and do this
hallway around the stone and you’ll pretty much find out where the center of
your stone is this works on bigger pieces of material in this case I use
another technique that I found very effective and that’s using the tops that
we dot these up with so I’ve got this larger bead op and I’ve put this
orthodontic wax in it or you can use clay this is available at any drugstore
this is just in there just to hold the stone while I chop it so you place this
and push it into the material Tran Center it a little bit now I’ve got a
adopt that’s close to the size of the stone I’m topping and I’m going to use
it to aid in centering the stone so now I can push this down on the stone
kind of Center it on there and you’ll see this stone is real close to the size
of this top you want to make sure your tops are not worn away because during
cutting some of them you’ll you’ll cut into the edge so you want to make sure
it’s good and round but now I can I can visually find the center of the stone by
setting it up on this top make sure that the flat you’ve cut on top of the stone
during preforming is set and flat against the dot and then just try and
center it on this top and once you found that it’s fairly well
centered just push it down a little harder into the material so it will stay
because now you’re going to have to change this dot to something smaller
typically half the size I mean the bigger it is the more support you give
to the stone but you can’t be too big because we’re not going to glue this
area of the piece which is very supportive but very difficult to remove
later with epoxy I’m just going to glue around the edge of it so I picked a dot
that’s about half the size of the stone and again the bigger the better but
you’ve got a glue it then and not have glue running over the edge so now you
can also check again with a millimeter gauge and check where the edge of it is
check both sides just to check make sure that your first centering was pretty
good and again just because I’ve got a flat
on this piece you know if this top has to be round again to Center the stone if
you’re going to use the top as as the support for the millimeter gauge so we
seem pretty close to Center and I found that this technique has worked very well
and I if you don’t get it centered you lose a lot of material when you’re
cutting so this is very critical that you get this properly Center so now
we’re going to blew it up and I use a two-part epoxy you just mix equal parts now use a toothpick to mix it and once you’ve got it well mixed now
we’re going to apply it around the edge of the stone or the dot you don’t want
it going over the edge of the stone this will cause problems later if it drips
over the edge and you cut into the glue it’s going to break that seal so you
want to get as much as possible on the stone without going over the edge of the
stone so once it’s on there I generally kind of rub it into the both the stone
and the dot and then manipulate it it’s going to
want to drip over the edge so you can for a couple of minutes you sit there
and play with it and keep it from going over the edge just by moving it around
you know you want it to spread out towards the edge of the stone but just
not over the edge again fit drips over the edge and you cut with a diamond lap
on it it’ll break that seal and the worst thing that can possibly happen to
you is this comes off the table so this glue is going to take five
minutes before it gets solid at all that you can even consider moving it but the
longer you wait the better you’re not going to want to cut on this really for
eight hours I have done it then as short as two or three hours but I think you
put yourself at risk of the stone breaking loose and not being solidly
attached so if you can wait overnight its best talking about the glue and it
going over the edge sometimes you’ll find that you you’re the stone you’re
cutting is that could be as big as you expect it to be and you’re going to
start running into the glue so what you’re going to want to do instead of
just cutting on a lap is take your exacto knife and just cut it back a
little ways so you’re not cutting into it because it can cause problems so wait
at least eight hours if possible before you start cutting on these stones so we
were topped up now and I need to wait a little while before I drop up the garnet
but you know this stone the citrine being around you don’t have to worry how
you put it in the transfer block but this is going to be a square so you’re
going to want to square it up appropriately when you top it up so when
you put it in the Machine your indexes are correct so as soon as this is
hardened up right wait till tomorrow and we’ll start cutting on the
this stone in the next part of how to cut gemstones

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