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The Portugese Cut
GemCad Derived Rendering by Bob Keller

Portugese Cut
GemCad Ray Traces for RI = 1.54   Zero Tilt
Random Model Cosine Model ISO Model
GemCad Ray Traces for RI = 1.97 (GGG)   Zero Tilt
Random Model Cosine Model ISO Model
The Portugese Cut
Angles for R.I. = 1.54 and up 161 facets + 16 facets on girdle = 177
16-fold, mirror image symmetry 96 index
L/W = 1.000 T/W = 0.434 T/L = 0.434 P/W = 0.585 C/W = 0.222 H/W = (P+C)/W+0.02 = 0.827 P/H = 0.707 C/H = 0.268
Vol./W^3 = 0.307 Brightness at 0° tilt R.I. = 1.54 COS = 48.5% ISO = 52.5%
Brightness at 0° tilt R.I. = 1.97 COS = 65.7% ISO = 76.7%
Pavilion
g 90.00 96-06-12-18-24-30-36-42-48-54-60-66-72-78-84-90 Cut to equal depth, establish size
p1 62.00 96-06-12-18-24-30-36-42-48-54-60-66-72-78-84-90 Meet g
p2 57.00 03-09-15-21-27-33-39-45-51-57-63-69-75-81-87-93 Meet g,p1
p3 52.00 96-06-12-18-24-30-36-42-48-54-60-66-72-78-84-90 Meet p1,p2
p4 47.00 03-09-15-21-27-33-39-45-51-57-63-69-75-81-87-93 Meet p2,p3
p5 42.00 96-06-12-18-24-30-36-42-48-54-60-66-72-78-84-90 Meet p3,p4 and at culet
Crown
c1 46.00 96-06-12-18-24-30-36-42-48-54-60-66-72-78-84-90 Meet g, cut level upper girdle line
c2 41.00 03-09-15-21-27-33-39-45-51-57-63-69-75-81-87-93 meet g,c1
c3 36.00 96-06-12-18-24-30-36-42-48-54-60-66-72-78-84-90 Meet c1,c2
c4 31.00 03-09-15-21-27-33-39-45-51-57-63-69-75-81-87-93 Meet c2,c3
c5 26.00 96-06-12-18-24-30-36-42-48-54-60-66-72-78-84-90 Meet c3,c4
t 0.00 Table Meet c4,c5

The Portugese Cut Design File is available for GemCad users.

The Portugese Cut is a popular and time honored design for larger stones. Due to its greater than normal depth it is best matched to stones of light to rather than dark color saturation. While the Portugese Cut has a large number of facets, it can be faceted using straightforward meetpoint technique. The high degree of symmetry and relative ease with which smaller facets can be polished make this design relatively fast to cut in larger stones. The visual effect of the Portugese Cut is often described along the lines of "swirling light".

I have a nice sized cylindrical chunk of clear GGG (gallium gadolinium garnet) RI = 1.97 beating around in my synthetics box that I think would wear a Portugese Cut well.

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