Faceting a Rectangle Gemstone
Devin guides you through step-by-step instructions for faceting a rectangle cut amethyst.
Step 1: Prep Gem Rough
Once you've picked your gem rough, you'll need to orient it for the best results when cutting. Whole chapters or books can be written on this topic, so we'll save that for next time! After orienting your rough, you'll cut a flat surface where the table will be. This will make it easier to apply dop wax and put the gem rough on a dop for cutting.
Step 2: Prep Alcohol Burner
Okay, most of you already know how to setup your alcohol lamp, but here it is for posterity. Put the denatured alcohol into the alcohol burner, put the top back on and light it up!
Step 3: Warm the Dop, Dop Wax, and the Rough
With the flame going, you can warm up the dop, warm up the rough a little bit not too much, and melt some wax onto the rough and onto the dop. Put the dop and the rough together at the waxy parts and precisely position the rough on the dop to cut for best yield.
Usually you'll start with a flat dop that attaches to the table of the stone. When you flip the stone over you may use a v-shaped dop or a cone-shaped dop depending on the design you're cutting and the shape that it gives the pavilion. Wait for the wax to completely cool. Once it is cool to the touch, very gently twist on rough and very gently tug it side to side to verify that the wax adhesion is strong enough for work.
It takes a lot of practice to really figure out how much twisting and tugging is just enough to verify the wax is on good, so don't give up, just keep trying!
Step 4: Put Dop in Quill
Now that your facet rough, dop wax, and dop are good friends, put the happy trio into the quill of your faceting machine. The quill is the liftable, turning, rotating, arm that holds the dop for cutting.
The cutting angle is determined by the faceting diagram you're using to cut your gem. At least I hope you're using a diagram! Otherwise you're doing an abstract and that works much better with an oil and canvas.
Consult your faceting machine owner's manual if you're having trouble figuring out how to set the cutting angle for your machine.
The indexes to cut to are determined by the faceting diagram you're using to cut your gem. Make sure you have the right index in the quill for the design you're cutting.
Lower the quill arm to the lap. Adjust the mast arm height to the proper cutting depth for the specific facet that you are cutting. You'll want to start by cutting less than what you need to start with. This is because you'll cut this facet again, with subsequently finer laps until you finally polish the facet. So you always leave a little bit more material at each stage so that by the time you polish you'll have just the right depth on the facet. Determining the right depth for each coarseness or fineness of cutting is another one of those lessons best learned through experience.
Step 5: Start Cutting
Okay, the cutting angle, the index and the mast height are set, and you've adjusted the height just right, right? Start cutting the stone but pressing lightly on the quill or the stone and moving it back and forth on the lap. This motion helps avoid overusing one area of the lap and getting a groove. When cutting the stone you'll start with a coarse grit and move to finer grits until you have a mirror finish on every facet. The cutting levels are generally called preforming to get the basic gem shape, prepolishing to put a finer cut on each facet, and then the polish. Choosing which grits to use to cut through each stage to the finished product is a very highly debated topic that is best left to each faceter's discretion. But if you're looking for an opinion, I use 600 grit, 1200 grit, then cerium oxide to polish quartz. For harder materials I use 600 grit, 3000 grit, then 14,000 grit or 50,000 grit. If I'm really trying to impress, then I'll touch each facet with 100,000 grit at the end. I've heard that the final polish should be alumina oxide since it is a finer grade than 100k diamond but I have yet to try it.
Step 6: Finished roughing in the main pavilion facet
The initial preform generally takes the first tier of facets or the median angle facet and cut until the facets meet at a point. This insures that there is enough gem rough to fully cut the design to the depth required. Technically you can save some rough by estimating or cutting exactly the amount needed to just allow the deepest tier of facets to meet but rarely is the rough so expensive to warrant saving a few points (one hundrenths of a carat) and going through that headache. Just cut till the facets meet and you'll have no worries!
Step 7: Closer look at the pavilion preform
Another look at the main facets on the pavilion meeting
Step 8: Polishing Quartz using cerium oxide
Once the three tiers of the pavilion have been preformed, then we will preform the girdle. The girdle is really important cause that is where gemstones are measured for setting in jewelry. Unless you're planning on never setting this gem or using custom jewelry, you will want to pull out your calipers to measure and cut the girdle to one of the major sizes that jewelry castings are available for. For example, 7x5mm or 8x10mm castings are widely available for oval or rectangle cuts.
Step 9: Closer look at the pavilion preform
The final polish for any gem requires special care. Unless you're an experienced faceter with plenty of broken in laps, you'll find this step will take a good bit of time and practice to learn. Any old hat who tells you otherwise... forgot!
You can polish with diamond, cerium oxide, alumina oxide, or any number of brand name polishing laps that take a lot of the thinking out of the process. Just depends on your preference. A general rule of thumb is that softer abrasives like cerium are used for softer materials and harder abrasives are used for harder materials like topaz and sapphire.
Professional and competition cutters will point out that ready to polish laps are softer and will round the facets on the gem when cutting. Harder laps that must be charged will cut flatter facets. Charging is when you put the diamond, cerium, or alumina powder, paste, or slurry onto the lap and wipe it into the lap.
How can you tell a facet has been rounded? Reflect the light from an unshielded 20 or 40 watt bulb onto the facet. Be sure to put the bulb label reflection in so that you can see it on the facet. If it is curved (beyond the bulb curvature) then it is rounded. Some rounding is so severe that the light reflection can not be seen on the entire facet at once.
Step 10: Smear the cerium oxide slurry on the phenolic lap
Once you have the dry cerium powder on the lap add water and smear the powder and water mixture on the lap. This is now called a slurry.
Step 11: No really, smear it good!
Here is another pattern of spreading the slurry on the lap. Please take care that you don't get too distracted finger painting in the slurry and forget to finish polishing your gemstone!
Step 12: Finished polishing pavilion of the gem
The pavilion of the gem has been polished using cerium oxide.
Step 13:Another look at the polished pavilion
Here is another view of the polished pavilion.
Step 14: Line up dop on transfer alignment fixture
Now that the pavilion is done, it is time to cut the crown. To do that we have to "flip" the rough on the dop and cut the other side. We have to remove the dop from the quill so that we can flip the stone over but you don't want to lose the positioning of the stone or it will be lopsided! We'll use a transfer alignment fixture to save our relative position so we can return to it after the transfer.
Set the cutting angle to 90 degrees and the degree to the starting degree for the design. That is usually the highest number of the index gear you're using. Lower the mast height until the girdle facet brushes smoothly across the transfer alignment fixture. Make sure you always use the same grit lap so that your alignment fixture doesn't contaminate your laps.
Step 15: Time to transfer from the pavilion to the crown of the gemstone
Remove the dop from the quill and put the dop into the dop transfer fixture. Pick out a dop that fits flush to the pavilion shape, in this case a v-shaped dop. You want a dop that is large enough to fully cover the culet and another tier or two of facets but not so large that it covers the girdle. When polishing the girdle we don't want to polish the dop too!
With the two dops in the transfer fixture, light up the alcohol lamp and warm the new dop and melt some wax onto it. I like to melt some wax onto the pavilion of the stone too, as that helps with adhesion. However be very careful not to heat the stone too much or the original wax on the table dop will melt and the stone will shift around losing its place. That can also lead to a lopsided gemstone.
With hot wax on the new dop and the stone's pavilion, push the two dops together firmly but not so much that you squeeze the wax out of the way.
Wait for the wax to completely cool. Once it is cool to the touch, very gently twist on rough and very gently tug it side to side to verify that the wax adhesion is strong enough for work.
It takes a lot of practice to really figure out how much twisting and tugging is just enough to verify the wax is on good, so don't give up, just keep trying!
Step 16:Remove the old dop from the stone
Wrap a wet paper towel around the gem rough and the new dop. Heat the far end of the original dop until the heat travels through the dop and slowly melts the wax holding it to the table of the stone. The weight of the dop will pull it down from the stone as the wax begins to give and you can remove the heat. Using another paper towel or an oven mitt, pull off the original dop from the stone and very carefully remove any wax that you don't want gumming up your laps while you cut the crown.
Step 17: Line up the dop in the quill to the transfer alignment fixture
Put the dop into the quill arm and lower the arm to the transfer alignment fixture. Gently turn the dop until the main girdle facet brushes smoothly across the transfer alignment fixture.
Step 18: Put the dop back in the quill to prepare to cut the crown of the gem
Once the alignment is done, tighten the screw in the quill to hold the dop firmly in place.
Step 19: Set the Cutting Angle for the Quill
The cutting angle is determined by the faceting diagram you're using to cut your gem. At least I hope you're using a diagram! Otherwise you're doing an abstract and that works much better with an oil and canvas.
Consult your faceting machine owner's manual if you're having trouble figuring out how to set the cutting angle for your machine.
Step 20:Each tier of the crown has been prepolished
I got ahead of myself! I meant to show you pictures of each tier getting preformed but I lost track of things and didn't come to my senses until just now. Here you see each tier has been preformed and prepolished.
Step 21:Put table adapter in quill and line it up
With the crown facets all done except for the table we don't have to worry about using the transfer alignment fixture. We can just take the dop out of the quill and put the table adapter into the quill. The table adapter is needed for some faceting machines because they can not support setting the quill angle to zero degrees for the table facet. The adapter allows you to set the quill angle to 45 degrees and the stone will be at zero degrees from within the adapter.
Rather than setting the quill angle to 45 degrees I prefer to put the adapter loosely into the quill, lower the mast height to the lap and when the adapter is flush to the lap and can be rotated smoothly, I tighten the quill angle screw, and then the quill screw for the adapter.
Step 22:Put dop in table adapter.
With the table adapter fully prepped, place the dop into the table adapter and tighten it. There is no need to align anything. Be sure to raise the mast height up or if you drop the quill arm you could pop the stone off the dop right before your very last facet!
Step 23: Cut the table of the crown of the gem
Now set the mast height so that you're cutting just into the table facet. Go slowly and cut cautiously so as not to over do it and put a big fat window into your gem and cut into the upper tier of facets.
Step 24:Finished prepolishing the table of the gem
The table facet has been prepolished.
Step 25: Finished polishing the table of the gem. A new gem is born!
The table facet has been polished and a new gemstone is born!
Step 26:Remove dop from table adapter
Take the dop out of the table adapter and see what time it is. Mostly likely you've gone way past your bedtime!
Step 27: Put dop in a dop holder
Put the dop in a holder so that you can melt the wax holding the gemstone onto it. I also recommend putting a wet paper towel around the stone to keep it cool.
Step 28:Heat dop wax to release gem
If you've heated the dop to melt the wax then you've got some extra wax on the gemstone you can probably peel off with your fingers. Nothing stronger than that should be used to avoid marring the polish or the edges of the gemstone.
Step 29: Remove excess wax from gemstone
If you've heated the dop to melt the wax then you've got some extra wax on the gemstone you can probably peel off with your fingers. Nothing stronger than that should be used to avoid marring the polish or the edges of the gemstone.
Step 30: Put gem into acetone to remove remaining wax
Put the gemstone into acetone to remove the rest of the wax. You can put the gemstone on a dop in the acetone too, but try not to leave the dop in too long or it could get a slight skin on it from the acid eating away at it.
Step 31: It really is in there!
Okay so my acetone is kinda dark and dirty but the gemstone is really in there!The finished gemstone
Hope you enjoyed the walk through!