Smithsonian Bar

GemCad Ray Traces for RI = 1.62
Random Model Cosine Model ISO Model

Smithsonian Bar
Designed by Jeff Graham
Angles for R.I. = 1.62 25 facets + 8 facets on girdle = 33
2-fold, mirror-image symmetry 96 index
L/W = 1.500 T/W = 0.862 T/L = 0.575 P/W = 0.482 C/W = 0.212 H/W = (P+C)/W+0.02 = 0.714 P/H = 0.675 C/H = 0.297
Vol./W^3 = 0.632 Brightness at 0 degrees tilt for RI = 1.62
COS = 75.7 ISO = 86.7
P1 47.00 96-48 Cut to center.
P2(G) 90.00 96-48 Cut a level girdle.
P3 70.78 24-72 Cut to whatever L/W desired.
P4(G) 90.00 24-72 Cut level girdle.
P5(G) 90.00 12-36-60-84 Cut corners, if desired...
P6 43.99 96-48 Cut equal step.
P7 41.00 96-48 Cut equal step.
P8 62.51 12-36-60-84 Cut to meet girdle, P1.
C1 72.00 96-48 Cut to meet girdle.
C2 45.33 12-36-60-84 Cut to meet girdle.
C3 28.00 24-72 Cut to meet girdle.
C4 18.00 24-72 Cut a level step, meet C2.
C5 8.00 24-72 Cut a level step.
T 0.00 Table Cut table same size as steps.

A bracelet featuring a tourmaline I cut to this design has been added to the Smithsonian Institution's collection and is on display in the Renwick Gallery in the Smithsonian.

The stone is a medium forest green tourmaline (with some blue over tones, flawless) 9.5mm x 16mm and weighs around 10 carats or so... The picture was taken for a show that was done for the Tucson Art Museum and does not really do the stone a lot of justice. That is where the curator of the Smithsonian first saw the piece and started talking to the jeweler about submitting it (and two other period pieces of his fathers's and grandfather's) for the Renwick Gallery in the Smithsonian.

The bracelet that the stone is set in is white gold, with the stone being tension mounted. I am currently scrambling to find another piece of tourmaline to cut a similar stone for the curator personally...

This cut is easy and can be almost any L/W with no changes. It works well in tourmaline that is dark or closed on the "c" axis. You can cut the corners in or leave them pointed, 2 cts and up.

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