The Pentafan Gemstone Design
The Pentafan is a unique cut designed for larger gems with deep color saturation. Learn how to cut this design that can make dark stones shine.
1 Minute Read
Flashes from a Dark Gemstone
To the right, you have an almandine garnet, one of the most difficult gemstones to facet for brilliance.
Even though the color saturation was quite deep, it turned out to be a great performer. There are continuous flashes of color as the gem is moved.
By bringing the pavilion facets to a point at the corners of the girdle, instead of at the culet, the play of light is greatly altered.
There is also a uniform dispersion of light throughout the stone, instead of the standard bright center surrounded by dark regions.
Diagrams
Pentafan Cutting Instructions
Pavilion
| Step | Angle | Index | Notes |
| 1 | 40º | 120-024-048-072-096 | Cut to PCP |
| 2 | 40.4º | 002-022-026-046-050-070-074-094-098-118 | Locate Corners |
| 3 | 41.5º | 004-020-028-044-052-068-076-092-100-116 | Meet P1, P2 @ Corner |
| 4 | 43.5º | 006-018-030-042-054-066-078-090-102-114 | Meet P1, P2, P3 @ Corner |
| 5 | 46.9º | 008-016-032-040-056-064-080-088-104-112 | Meet P1, P2, P3, P4 @ Corner |
| 6 | 61º | 012-036-060-084-108 | Meet Others @ Corners |
| 7 | 90º | 012-036-060-084-108 | Set/Level Girdle |
Crown
| Step | Angle | Index | Notes |
| 1 | 19º | 120-024-048-072-096 | Set Girdle Thickness |
| 2 | 45º | 012-036-060-084-108 | Level Girdle |
| 3 | 12º | 006-012-018-030-036-042-054-060-066-078-084-090-102-108-114 | Meet C1, C2, C1 form TCP |
| 4 | 0 | Table | Meet C3, C1, C3 |
A note from Donald Clark: D. R. Jerkins apologized that he couldn't send us an example of the Pentafan gem design sooner. As it turned out, the gems sold out too quickly. Now that's a problem we should all have!
D. R. Jerkins
Related Articles
Rattle 2 Bead: Faceting Design Diagram
Scholar: Faceting Design Diagram
Budgy: Faceting Design Diagram
Circle: Faceting Design Diagram
Latest Articles
Precision Faceting a Story Gemstone: Choosing Rough
32 Green Gemstones (How Many Do You Know?)
A Guide to Antique Georgian Jewelry
Hambergite Value, Price, and Jewelry Information
Never Stop Learning
When you join the IGS community, you get trusted diamond & gemstone information when you need it.
Get Gemology Insights
Get started with the International Gem Society’s free guide to gemstone identification. Join our weekly newsletter & get a free copy of the Gem ID Checklist!