Precision Gem

The Making of a Masterpiece

I get asked to cut a square step quite often, while they take longer to cut than most other stones, and for some reason are not as fun, they always look great with the right rough. I thought I would photo document the cutting of one. This one is being cut for a client from a piece of Pink Tourmaline from Africa. The stone wasn't really shaped the best for this style cutting, however that is what the client wanted.

This first photo is of the stone after a small amount of preforming, held on the dop with wax. I don't do a lot of preforming, some cutters do, I just don't see the point in it. I basically clean up the stone a bit to the rough shape, and then cut a flat spot where the stone will be held to the dop.

This stone weight 12.1 ct in the rough before any pre shaping. I most likely ground off about 2 cts to shape it for dopping.

Here the stone is shaped a bit more, so I can get an idea of where the girdle will fall. At this point the stone was about 9.5 mm. I eyeball cut in the corners, making them a bit shallow to make sure I don't over cut them.

It's now time to start cutting in the pavilion facets. First I cut in the culet which is the lowest angle on the stone. To shape it in, only the 4 longer sides are cut, this speeds things up a bit, as with step cuts you never get this right the first time, and end up going up and down all the steps at least 2 times with the rough lap.

I do all the roughing in on a stone this size with a 260 grit diamond lap. It leaves a very frosted finish and is hard to see the facet lines, but at this point removing a lot of material is what is needed.

Things are starting to take shape now, and I notice the size needs to be brought down a bit. At this point I switch to a very well used 360 lap, which cuts finer, and recut everything, adding in all 5 steps. This cut has 5 steps on the pavilion. On smaller stones it's common to reduce this to 4 steps.

The black marks you see on the facets are drawn on with a marker. These help me see the facets lines as I cut the next tier. At this point the stone is finished being roughed in with the 360 lap. The next step will be to recut the whole stone, this time with a 600 grit Nu-Bond lap. This lap cuts very fine, more like a 1200, leaving a finish that can be polished.

One last photo of the stone in the roughed in state showing more of the faceting machine. Basically what the machine does is hold the stone. You see the large protractor scale in the background, that is used to set the angle of the cut. Right now the machine is set for 90 degrees for cutting the girdle. To the bottom right of the picture on the quill, is an index gear. You can't really see in in the photo, but this sets the index or rotation of the stone. This gear used for this cut has 96 teeth, but the design only requires 8 teeth: 96, 24, 48 and 72 for the main facets, and 12, 36, 60 and 84 for the corners.

Here's a view of the index gear. The knurled knob on the right is what's called a "cheater". This allows you to cut in between teeth by rotating the knob.

The stone is not completely recut with the 600 NuBond lap. This leaves a very fine finish, ready to be polished, and all the meets are cut in perfectly at this stage.

The polishing of the pavilion starts now. Since the previous lap cuts so smooth, I go right to a 100,000 grit polish on a Batt lap. The Batt polishing laps are the finest laps you can buy. They are harder than most other laps which makes a flatter facet with sharper edges. You'll so most commercial stones are cut on softer laps, and the facet edges have a slight rounded look to them, and since they are doing finial cutting and polishing in on step, a much coarser polish is used. Typically a polish around 8000 grit or even coarser is used. The trained naked eye can see the polish scratch marks from such a coarse polish.

Polishing a blind of science, art and witch craft. A technique that works for one person doesn't work for another, but every cutter agrees a good polish makes the stone pop. The Batt lap is wiped with a very very fine layer of cutting oil, then a touch of the diamond powder is spread around on the lap. The diamond gets actually impressed into the surface of the lap, every stone or two, the lap needs to be recharged.

The stone is now finished polish and in the transfer fixture. The purpose here is to get the stone of the one dop, and onto another one so that the crown can be cut. The second dop is shaped like a cone. The fixture holds the stone perfectly aligned. I have switched from the over to using epoxy on most stones. Previously I was part of the dark side using hot wax. Wax has it's advantages, but also drawbacks.

Once glue is fully cured (20 hours - this is the drawback) I gently heat the initial dop to soften the wax, then remove that dop. The stone is now ready for the crown to be cut. Cutting the crowns is typically much faster then the pavilions especially on Asschers since the size is now all set, and there are only 4 angle changes on the crown.

Above right the first tier of facets is roughed in. This sets a level girdle and lets me make sure I have room to get the crown in with needing to adjust the crown angles. In many commercial cut stones, the crowns are very flat. This reduces the dispersion and sparkle of a stone, and gives is a lifeless look. You can often save weight and maintain a larger face up size with a flat table, but the stone suffers from it.

Above the stone is finished being cut with the 600 NuBond lab, and the picture on the right has the first tier of facets polished. Notice that the table is cut in. The faceting machine I use is on of the few that are able to cut the table with out taking the stone out of the machine and using a 45 degree adapter.

The stone now is finished and taken out of the dop. Again a little heat to the dop makes the epoxy let go.

A little clean up with rubbing alcohol, and the stone if finished!

The stone finished up to be 4.62 cts. and measures 8.99 mm. This is larger than I had originally thought, I had figured it would be under 4 cts closer to 3. I hope the client is not upset with the size.