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| Gram Portuguese - designed by Jeff R. Graham jeff@faceters.com ©2002 | |
|---|---|
| Angles for R.I. = 1.76 | 145 facets + 16 facets on girdle = 161 |
| 16-fold, mirror-image symmetry | 96 index |
| L/W = 1.000 T/W = 0.461 T/L = 0.461 P/W = 0.452 C/W = 0.186 | H/W = (P+C)/W+0.02 = 0.658 P/H = 0.686 C/H = 0.283 |
| Vol./W^3 = 0.242 | Brightness at 0 degrees tilt for R.I. = 1.76 80.2% Light Return |
| Pavilion | |||
|---|---|---|---|
| P1 | 51.22 |
96-06-12-18-24-30-36-42 |
Cut to center point. |
| P2(G) | 90.00 | 96-06-12-18-24-30-36-42 48-54-60-66-72-78-84-90 |
Cut a level girdle, meet P1. |
| P3 | 47.26 | 03-09-15-21-27-33-39-45 51-57-63-69-75-81-87-93 |
Cut to meet girdle. |
| P4 | 43.24 | 96-06-12-18-24-30-36-42 48-54-60-66-72-78-84-90 |
Cut to meet P1. |
| P5 | 39.15 | 03-09-15-21-27-33-39-45 51-57-63-69-75-81-87-93 |
Cut to meet P3. |
| P6 | 35.00 | 96-06-12-18-24-30-36-42 48-54-60-66-72-78-84-90 |
Cut to meet P4. |
| Crown | |||
|---|---|---|---|
| C1 | 39.00 |
96-06-12-18-24-30-36-42 |
Cut to meet girdle. |
| C2 | 35.09 | 03-09-15-21-27-33-39-45 51-57-63-69-75-81-87-93 |
Cut to meet girdle. |
| C3 | 31.24 | 96-06-12-18-24-30-36-42 48-54-60-66-72-78-84-90 |
Cut to meet C1. |
| C4 | 27.44 | 03-09-15-21-27-33-39-45 51-57-63-69-75-81-87-93 |
Cut to meet C2 |
| T | 0.00 | Table | Cut to meet C3, C4. |
Gram Portuguese - Cutting Remarks
This is my recalculation of the old traditional style "Portuguese" cut. This cut has been around a very long time and is cut all over the world. The main drawback when you cut this design using traditional angles are that the stone always has a fish eye in low refractive indexes, and in higher indexes the old angles could be much better performance wise.
So here is a Portuguese (I am naming it Gram Portuguese so that there will be no confusion with the old design) that I have optimized and I think it works very well in light colored material. If you are lucky enough to get a Zircon large enough for this design it is a knock out. YAG, CZ, and man-made Sapphire are all good materials for this design.
I suggest a light colored material and obviously a larger stone for this design. Cut this in refractive indexes 1.76 to 2.14 with no changes. There is a lot of dispersion in this design when it is cut and it cuts easily although it is a lot of work.
Enjoy cutting your "Gram Portuguese"... Drop me an email to let me know your results and what you've cut, or feel free to inquire if you have any questions or need some help regarding this design.
Random - Cosine - ISO
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