| Barion Old Mine by Bob Keller 11-98 | |
|---|---|
| Angles for R.I. = 1.54 | 73 facets + 12 facets on girdle = 85 |
| 4-fold, mirror-image symmetry | 96 index |
| L/W = 1.000 T/W = 0.577 T/L = 0.577 P/W = 0.511 C/W = 0.168 | H/W = (P+C)/W+0.02 = 0.699 P/H = 0.731 C/H = 0.241 |
| Vol./W^3 = 0.279 | Brightness at 0 degrees tilt for R.I. = 1.54
COS = 66.4 ISO = 71.4 |
| Pavilion | |||
|---|---|---|---|
| m | 42.00 | 96-04-08-12-16-20-24-28-32-36-40-44-
48-52-56-60-64-68-72-76-80-84-88-92 | Cut to permanent center point |
| g1 | 90.00 | 12-36-60-84 | establish corners, girdle line |
| g2 | 90.00 | 02-22-26-46-50-70-74-94 | meet g1,m |
| b1 | 75.25 | 02-22-26-46-50-70-74-94 | level girdle, meet g1,m |
| b2 | 70.39 | 96-24-48-72 | meet g2,b1 and m,b1 |
| Crown | |||
| s1 | 45.00 | 02-22-26-46-50-70-74-94 | level girdle, meet g1, g2 |
| s2 | 46.00 | 12-36-60-84 | level girdle meet s1 g2 |
| s3 | 35.00 | 02-22-26-46-50-70-74-94 | cut until width of s1 approx = W/10 |
| s4 | 36.00 | 12-36-60-84 | meet s3, s1 |
| s5 | 20.00 | 02-22-26-46-50-70-74-94 | meet s4 points |
| d | 39.63 | 96-24-48-72 | Cut short of meeting g2 and s5 |
| t | 0.00 | Table | level table, leave a little s5 |
I designed this cut for a squarish piece of amethyst that had a nice color but was a little on the light side in terms of saturation. I wanted something that would be relatively easy and quick to cut, and which would have the effect of making the material appear to be more deeply color saturated than it really was, but still have a good play of light.
My initial idea for the stone was to use barion facets to mate the pavilion to a 24-sided, cushion shaped crown with 3 or 4 tiers of step cuts around. However, a desire to cut something quicker prevailed, and since I've always thought the old mine shape was attractive, I decided to try it. I also wanted to be able to mount the stone in a standard 4-prong finding, hence the cut corners. I'd guestimated a little larger stone than 14mm across the corners, but after I got finished cutting away a late discovered and deceptively deep flaw, 14mm it was.
The pavilion-up image at right gives an idea of the actual color saturation of the rough. I got the color deepening effect I needed, and I was also pleased with the dispersion - the stone shows some nice red and violet flashes.
This design is pretty straight forward to cut. After cutting the pavilion mains, the g1 girdle facets are cut to an equal depth, determining the size of the stone and establishing a level girdle. The b2 facets will cut in very quickly, so exercise care with them. I cut the b2 facts on my stone by hand wiping it across a stationary 1600 lap. They could be skipped if you're so inclined. If you leave them out, the b1 barion moon facets will form a scalloped shape, which just looks a little less finished to my eye.
Note and keep in mind that the g1 corner girdle facets are cut at a different elevation than the g2 girdle facets, and that the s2 and s4 corner crown facets are cut at a different angle and elevation than their s1 and s3 counterparts.
The crown is an easily embellished step cut. It's important to establish a level girdle after you transfer, or you'll wind up cheating yourself blind trying to make the step facets parallel and get their junctions to meet. Since my stone turned out to be smaller than I had initially planned, I decided during cutting to make the step cuts somewhat wider than shown in the diagram, with the effect of increasing the depth of the stone, reducing the size of the table, and further deepening the color. I tend to like larger tables, and I like the relative proportions of the step and table facets widths better as designed and shown in the diagram. You can tangent ratio the crown angles if you want to increase its depth and maintain the proportions as shown.
If you're comfortable 'floating in' facets, you might find it less demanding cutting to use a sequence that floats in the s4 facets to meet the s5 facets after they are cut.
If you cut a Barion Old Mine, let me know what you've cut it in and your results. Enjoy!
