Fundamentals of Lapidary
By Donald Clark CSM
International Gem Society
- Faceting is a marvelous amalgamation of engineering
and art. Through a mechanical process of cutting facets on a piece
of crystal, marvelous gems are created.
- To the uninitiated, faceting appears to be the apex of complexity,
but that is not the case. Faceting has its complex areas, like competition
cutting and design, but one does not need to enter these areas. Learning
the standard cuts is within the reach of almost everybody. The primary
requirements are a desire to learn and the ability to follow instructions.
- To unravel the mysteries of faceting, we will describe the actual
cutting process. The material is not important; the procedures
are the same for
amethyst, emerald, or any other gem material. There are several
steps, but none of them are particularly complicated. Once you see
it is, you will understand that it is something you can do!
... There are three basic elements to arranging the
facets on a gemstone. They are: 1) the angle of the cut, 2) the rotation of the
gem, and 3) the depth of cut. These three settings precisely locate every facet
on a gem. How to make the adjustments varies slightly from one machine to another.
However, all machines work on the same principles and there are only subtle variations
on how to make the
... When cutting a gem, the design instructions tell
you the index and angle for each facet. There is no guessing. The depth of the
cut will be obvious when cutting. If your facets do not come together, you need
to cut them deeper. If you cut them too deep - well, all beginners need to learn
to use a light hand. Correcting over cut facets requires recutting the previous
stages to the new depth. Hence the saying, "Cut a little,
look a lot."
... The angle of your cut is set on a protractor,
or read off a digital display. How to set the angle varies slightly with the
different machines. Sometimes it is a matter of loosening a setscrew, adjusting
the angle, then retightening the screw. On other machines, it involves turning
a handle until you reach the proper angle.
... The index gear controls the rotation of the gem.
They are available in a variety of sizes, but 64 and 96 are the most common.
To set the index; you release a pin, rotate the gear to the properly numbered
slot, then let the pin return to its holding position.
... This is actually called a "height setting," but
it serves the purpose of determining how deep each facet is cut. While there
are variations in how this is done on different machines, the principals remain
the same. A coarse adjustment brings your setting in close, and then a fine control
makes the final setting.
... Due to subtle variations in your equipment, you
will occasionally have a facet that will not lay flat on the
polishing lap. A "cheater" control makes subtle, side-to-side adjustments. These
are less than a full index number.
... Water, (often with additives,) is used as a lubricant.
Each machine has a method of wetting the cutting laps. The most common is a simple
drip tank. Its beauty lies in its simplicity. Simply open the valve to where
you get a few drips per second. You want just enough to keep everything damp,
without excessive splashing.
... Each machine has a method to control the speed
of the laps. Many will also allow you to reverse the direction of rotation. As
a rule, use higher speeds with coarse cutting, slower
speeds when polishing.
... Laps are disks with abrasives on the surface.
They are usually metal charged with diamond, but other materials and abrasives
are used. They go on a revolving platform and are changed as
... The cutting and polishing procedure is done in
stages. It begins by removing the excess material with a coarse lap. Next, the
scratches are sanded out with a finer lap. Finally, a polishing lap is put on
the machine for finishing.
... Now that you know what the controls
are, we will go through the procedures for a standard, round brilliant cut. First,
inspect the gem to make there are no fractures that will cause problems. Then
attach the gem to a dop stick and insert it in the faceting machine.
... The dop is free to swing side to side during cutting,
or lifted for inspection. It is the angle setting that limits the downward swing.
It is important to understand this, because an under or over cut facet will not
be at the proper angle. This
is called a "hard stop" and is on almost all machines. The Facetron has no stop
and you need to modify your technique to suit this machine.
Cutting the Main Facets
... Place a coarse cutting lap on the machine. Set
the speed to medium and turn on the water. Get the lap thoroughly wet, spreading
the water with your fingers if necessary, then
turn everything off.
... Look at the instructions to the right. We have
eight pavilion main facets cut at 42 degrees. Set the angle on your machine to
42 degrees. They are cut at index settings 96, 12, 24, 36, 48, 60, 72, and 84.
Set the index on your machine to 96 for the first
... Adjust the height so the stone will just meet
the lap. This will not be deep enough, but it is the proper place to
... Now, turn the water and machine on again. Gently
introduce the stone to the lap and sweep it back and forth across the surface.
Do not use much force; apply just enough pressure to keep the stone in contact
with the cutting surface. When you have cut all the way to your depth setting,
the sound will change. It will go from a grinding noise to a 'shhh" sound. If
you are using light enough pressure, it will be a clicking sound as just the
largest particles of abrasive touch the gem. This technique is called "Cutting
by sound." It is a valuable skill to develop, so pay attention to it right from
... When your first facet is cut, turn the gem over
to the opposite index setting, 48. Repeat the cutting procedure until the facet
is fully cut to the selected depth.
... Now look at your stone. Do the two facets you have cut
come together in the center? If they do, you set your machine too deep. Bear
this in mind for the next stone, as you do not want to remove too much material
in the initial stages.
... You should see two flat surfaces on an otherwise
rough shaped piece of material that do not come together. Lower the head a bit
and cut both facets again. Repeat this process of lowering the head and recutting
the facets until they meet in the center. With practice you will get quicker,
but you need to start on the conservative side so
you learn not to waste material.
... Once you have your depth set properly. Cut the
remainder of the pavilion main facets at index settings 12, 24, 36, 60, 72, and
84. If you find that one of these facets does not reach the center, or has an
uncut shallow area in it, lower the stone again. Recut all the main facets at
this new depth setting.
Cutting the Girdle
... For the next step, you will cut the girdle. Adjust
the angle setting to 90 degrees. This puts the gem parallel to the lap. Your
machine will have an opening in the splashguard, or a means to hold it out of
the way while cutting the girdle. Do this now. Set the index to your first setting,
which is 2. Now, carefully lower the gem until it
just touches the lap.
... Turn the machine and water on. Cut the first three
facets at indexes 2, 10, and 14. They are small and will not need nearly as much
cutting as the main facets did. When finished, inspect your gem to see if these
facets come together. If they do not, then you will have to lower the head. When
the depth is set, continue cutting at the other index settings. You will probably
come to an area that is shallower than the rest of the stone. Lower the gem until
you can cut the girdle facets at this section. You have now found the minimum
distance you need to cut. Go back and
cut all the girdle facets to this depth.
... You have now shaped the pavilion of the gem. However,
the coarse lap has left a very rough surface. You cannot see it, but there are
tiny, subsurface fractures as well. You need to smooth the surface before you
can polish the gem.
... Remove the coarse lap from the machine.
Clean the gem and all the controls with a damp cloth. This will remove any coarse
particles that could contaminate your prepolish lap. You do not want to learn
this lesson the hard way! Contamination is a very serious problem, but one that
is easily avoided.
... Place the prepolish lap on your machine and wet
it. You ended your last sequence by cutting the girdle. Since your machine is
already set at 90 degrees, it makes sense to prepolish the girdle first. Set
the index to 2.
... Setting the height accurately is very important, as
you are only removing a tiny amount of material in this step. Begin by setting
the height so the stone just barely touches the lap. Many, (if not most machines,)
will not have the lap perfectly level to the swing of the dop. If this is the
case, adjust your height so the gem first touches the lap in line with the center.
For accuracy, always stop cutting at this line.
... Using the fine adjustment, lower the gem just one tiny
increment. Prepolish the first facet, being careful to stop on your centerline.
Now inspect the facet. It should have a smooth, frosted surface, with no visible
pitting. If not, lower the gem just a tiny bit more and cut it again. Once you
have the depth set correctly, prepolish the remainder of the girdle facets. Listen
carefully and you can hear when the cutting stops.
... The next step is to prepolish the main facets. Set your
angle to 42 degrees and the index to 96. Adjust the height so the gem barely
touches the lap on the centerline. Lower it one more tiny increment. Now proceed
with prepolishing the mains, just as you did with the girdle facets.
... Now it is time to cut the break facets. They were not
cut in the coarse stage, because they are so small. Your main facets are cut
at 42 degrees and the break facets are cut at 43.7. That is just a tiny
... To cut the break facets, set the angle to 43.7
degrees and the index to 2. Adjust the height so the gem barely touches the prepolishing
lap. Very gently, cut two facets at index 2 and 10. The technique is to introduce
the gem to the lap with a very light hand and bring it towards the centerline.
It should only take a couple swings of the dop to cut
... When fully cut, they will create a level girdle
and come together in the center. However, they should not come together yet.
Lower the head just a bit and cut them again. Repeat this process until the facets
come together properly. When the height is set correctly, cut the remainder of
... Inspect your progress frequently. One of the most
difficult aspects of faceting is learning hand control. Even though your machine
is properly set, you can under or over cut small facets. From the beginning,
pay attention to the hand pressure you are using. Learning to use consistent
pressure is the key to getting uniform facets.
... Before polishing, remove the prepolishing lap;
thoroughly clean your hands, the gem, (especially the area it where it attaches
to the dop,) and the machine. Again, contamination is a serious problem, but
one that is easily avoided.
... Now put your polishing lap on the machine. The techniques
for preparing the laps vary with the materials used. However, once set up, the
process remains essentially the same.
... You finished the prepolish step with the break
facets. Since your angle is already set for them, it makes sense to polish them
first. Set your index to 2. Adjust the height so your facet just barely touches
the lap on the center line. Turn on the water, (if used,) and set the speed to
... Introduce your facet to the lap very gently and
polish it for about three seconds. Now, pick up the stone and inspect your polish.
It may be incomplete, which simply requires a few more seconds on the lap. However,
you may find that the polish is not completely covering the facet. In that case,
you will have to make some subtle adjustments to get a perfect alignment. The
cheater control adjusts the alignment from side to side. The angle controls the
facets up and
... There is a simple rule to making these adjustments.
When you lift a stone to inspect it, make your adjustment to the direction opposite
of where it needs polishing. To test your alignment, paint the facet with a felt
tip marker. Give it a second to dry and then rub the facet on your polishing
lap. If the ink is removed across the entire facet, your adjustment is correct.
If not, make the necessary
... When you have your facet properly aligned,
repeat the polishing process. Check your progress every three to five seconds.
You can over cut small facets in the polishing stage, so be conservative and
do not hurry. Repeat this process on the other break facets.
... After your break facets are polished, move on to the
pavilion mains. The procedures remain the same, but they will take a little
longer to polish. Make your inspections every five to ten seconds.
... To polish the girdle facets, set your machine to 92
or 93 degrees. This purposely sets the machine so only the edge polishes. There
is no need to polish the entire surface, as most of it will be cut away in
the next step. When polishing, inspect the facets every couple seconds. They
are tiny and polish rapidly.
Cutting the Crown, Initial Steps
... The procedures for cutting the crown are nearly
identical to cutting the pavilion. However, there are two additional steps. Before
cutting the crown, the gem needs to be turned over, to be dopped on the other
side. Every faceting machine comes with a transfer fixture, so this can be done
accurately. See the article on "Cold Dopping
your machine instructions for details.
... Place the new dop in the machine. If you do not
have a keyed dop system, set the index to 2 and leave the angle at 90 degrees.
Lower the head until you can lay a girdle facet flat on the polishing lap. Now
tighten the dop.
... Set the index to 96 and look at your stone. It is properly
oriented if the peaks of the main facets are aligned straight up and down. If
they are slightly cantered, set the index to 2 and place the stone on the lap
again. Loosen the dop and rotate the stone to one of the adjoining facets. Tighten
the dop again. There are only two ways of orienting the stone, so it has to be
correct after this adjustment.
Cutting the Crown Main Facets
... Place the coarse lap on the machine and set the
angle to 35 degrees. Set the index to 96 and adjust the height so the stone barely
touches the lap.
... This facet determines the thickness of the girdle. When
the gem is finished, the girdle should be about 3% to 4% of the diameter of the
gem. For example, if your stone measures 6 mm in diameter, the girdle should
be between .18mm and .24 mm, or roughly 2/10 mm. After cutting this facet, you
are going to have to prepolish and then polish it. Both of these steps will remove
more material. For this stage, you want to stop cutting about twice the size
your finished facet, or about 4/10 mm.
... Cut this facet and then lower the height. Keep
adjusting the depth setting until you reach the proper depth. Then cut the remainder
of the crown main facets.
... Clean the gem and the machine and put the prepolishing
lap on the spindle. The angle is already set for the mains, so simply set the
index to 96 and adjust the height so the gem barely touches the lap. Prepolish
the first facet and inspect it to make sure
you have removed all the coarse scratches.
... Now look at your girdle thickness. It has changed
from the first cutting and will change very little when polished. Is it pretty
close to the thickness you want? If not, you can cut it a little deeper. If you
are not certain, then simply stop. It is better to have a girdle that is a bit
too thick than too thin. (Thin girdles are prone to break when a goldsmith tightens
the prongs against
... When the mains are prepolished, set the angle
to 37.5 degrees and the index to 94. Lower the head until the stone barely touches
the lap. Cut the first two break facets at indexes 94 and 2. Lower the head as
needed until the break facets create a level girdle and come together in the
center. Then cut the remainder of the sequence, checking your progress
... With the prepolish lap still in place, set
the angle to 16 degrees and then adjust your height setting until the stone
barely touches the lap. Cut the first two star facets at index setting 90 and
6. Adjust your height setting until they almost touch the top of the break
facets. (They will enlarge slightly when polished, so leave a wee bit of room.)
Then cut the remainder of the star facets to that depth.
... Now it is time to polish the crown facets. Clean
the machine thoroughly and place a polishing lap on the spindle. The angle is
set for the star facets, so polish them first. Polish the main facets next and
finish with your break facets. You may find that your points do not come together
as accurately as the diagrams. You can make fine adjustments with the polishing
lap, but do not worry about it. This is your first faceted gem and your priorities
are learning the sequence. Your technique
will improve with experience.
... The final step is to cut the table. For this,
you need to use the table adapter that came with your faceting machine. Set the
angle to 45 degrees and place the table adapter where the dop usually goes. The
dop goes in the table adapter, which holds the gem
perpendicular to the lap.
... Put a coarse to medium cutting lap in the machine,
depending on how much material you need to remove. Set the height to make a small
cut. Gradually lower the height setting, cutting a progressively larger table.
As the table grows, you may find that it is not level, that it is not approaching
the top of the main facets equally. The procedure for aligning the table is much
like aligning for polishing. If it needs to cut more towards the top, lower the
angle a bit; if it needs to go to the right, turn the cheater control to the
left; etc. This is simple, always adjust the to the opposite side. The more accurate
your machine is, the less
likely you will have to make any adjustments.
... Cut the table until it nearly touches the juncture
of the break and main facets. Switch to the prepolish lap and bring it in just
as close as you can. Finish by
polishing the table.
... Now, do you think you could do that? Of course
you can! There are several steps to put 57 facets on a gem, but none of them
are difficult. You will find that your first stone is the hardest, because
you have to learn all the new controls and procedures. It will take you six
to eight hours. With practice, the time will come down to an hour or two.
... Once you are familiar with your faceting machine, you
can move on to other shapes. Soon you will be faceting like a professional.
In fact, your gems will be better cut than the majority of stones you see in
the jewelry stores. Those are cut with methods that give emphasis to speed
rather than accuracy. You can do better work than most full time lapidaries!
Your gems will have higher value because of the precise cutting and you can
take pride in work well done.
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