The Fan Shield Cut For Gemstones


The Fan Shield cut is designed to bring out maximum brilliance from deeply color saturated gem material. Like the Pentafan design, this cut does a superb job. The technique of bringing the pavilion facets together at the corners, rather than the culet, works wonderfully.

I cut two stones from the same garnet for comparison. One was cut as a Fan Shield. The other was cut as a standard round brilliant. Both were around 12 mm across, cut with low crown and pavilion angles.

Fan Shield Cut - Garnet
Garnet with Fan Shield cut

The round gem performed predictably. It was mostly dark, with occasional flashes of light. Directly under the table, the Fan Shield cut gem was fairly subtle. However, it was hard to concentrate on that. All around the edges, light flashed constantly. The subtlest movement caused a myriad of changing reflections, creating one of the liveliest stones I’ve ever seen.

For the faceter, this design allows higher yield in dark gems without sacrificing beauty. Furthermore, this cut was designed to be worn. Set on a ring, a Fan Shield cut gemstone will dazzle everyone in sight.

Fan Shield Cut: Diagrams

Fan Shield Cut - Diagrams
Fan Shield Cut. D. R. Jerkins, Designer.

Fan Shield Cut: Instructions

  • 96 Index Angles for RI 1.77
  • 64 facets + 6 on girdle = 70
  • L/W = 1.073 T/W = 0.549 T/L = 0.512
  • P/W = 0.416 C/W = 0.113 H/W = 0.549
  • P/H = 0.758 C/H = 0.205

Girdle

Step Angle Index Comments
G 90º 06-26-38-58-70-90 Determine stone size

Either crown or pavilion may be cut first after the girdle is cut.

Pavilion

Step Angle Index Comments
1 40.0º 96-32-64 Cut to PCP
2 40.7º 02-30-34-62-66-94 Meet P1 @ Girdle
3 43.2º 04-28-36-60-68-92 Meet P1, P2 @ Girdle
4 46.0º 05-27-37-59-69-91 Meet P1, P2, P3 @ Girdle
5 53.2º 06-26-38-58-70-90 Meet P1, P2, P3, P4 Level Girdle
6 37.2º 16-48-80 Meet P5 @ Girdle & P1, P2 near Culet

Caution: Take extra care to make facets P1 through P5 point up at the girdle. Otherwise, facet P6 won’t reach the appropriate P1, P2 meet point. This will result in a significant loss of scintillation due to proportional misalignment with the crown facets.

Crown

Step Angle Index Comments
1 19.0º 14-18-46-50-78-82 Cut to same mast height, Set girdle thickness
2 20.5º 11-21-43-53-75-85 Meet C1 @ Girdle
3 22.9º 09-23-41-55-73-87 Meet C1, C2 @ Girdle
4 28.3º 07-25-39-57-71-89 Meet C1, C2, C3 @ Girdle
5 36.3º 06-26-38-58-70-90 Meet C1, C2, C3, C4 Level Girdle
6 30.1º 96-32-64 Meet C5 @ Girdle
7* 0.0 Table Meet C3, C4, C6, C4, C3

* Note: Tests have shown that a table that rests slightly higher than this meet point gives optimal brightness, but only by about 2%.