The Petaluma_80 is a striking pentagon-shaped faceting design that offers exceptional optical performance and unique 5-fold radial symmetry. Tailored for an 80-index gear, this design brings out dynamic reflection patterns, making it an outstanding choice for custom gemstone cutters.
Optimized for Quartz (RI = 1.540), Petaluma_80 also works brilliantly on materials with higher Refractive Indices, such as Topaz, Tourmaline, Beryl, and Sapphire.
Design Specifications
| Parameter | Specification Details |
|---|---|
| Design Name | Petaluma_80 |
| Target RI | R.I. = 1.540 (Quartz & higher) |
| Facet Count | 51 facets + 5 girdles = 56 total |
| Symmetry / Index | 5-fold radial symmetry | 80 Index Gear |
| Proportions | L/W=1.051 | T/W=0.333 | U/W=0.317 P/W=0.436 | C/W=0.230 |
| Volume Ratio | Vol./W³ = 0.231 |
Step-by-Step Cutting Angles
1. Pavilion Cutting Sequence
| Facet | Angle | 80-Index Settings | Instruction / Meet Point |
|---|---|---|---|
| 1 | 90.00° | 80-16-32-48-64 | Set size |
| 2 | 45.29° | 80-16-32-48-64 | Temp CenterPoint |
| 3 | 41.50° | 02-14-18-30-34-46-50-62-66-78 | Meet girdle, CTP |
| 4 | 43.20° | 80-16-32-48-64 | CTP |
2. Crown Cutting Sequence
| Facet | Angle | 80-Index Settings | Instruction / Meet Point |
|---|---|---|---|
| A | 57.41° | 80-16-32-48-64 | Set girdle thickness |
| B | 48.25° | 01-15-17-31-33-47-49-63-65-79 | Meet girdle, A |
| C | 30.00° | 14-30-46-62-78 | Floating - no meets - (stop before meeting A, B) |
| D | 19.78° | 13-29-45-61-77 | Meet B, C |
| E | 15.59° | 12-28-44-60-76 | Meet C, D |
| F | 0.00° | Table | Meet D, E |
Recommended Gemstones
Petaluma_80 is highly versatile and accommodates various rough gemstones:
- Quartz Group (RI 1.544 - 1.553): Amethyst, Ametrine, Citrine, and Rose Quartz.
- Beryl Group (RI 1.577 - 1.583): Aquamarine, Heliodor, and Morganite.
- High RI Gemstones: Topaz, Tourmaline, Garnet, and Sapphire for maximum optical dispersion and brilliance.
Pro Cutting Tips & Insights
- Gear Index Requirement: Ensure your faceting machine utilizes an 80-index gear, as the 5-fold radial symmetry relies strictly on this indexing.
- Floating Facet C: Crown Facet C (30.00°) is a floating facet. Take extra care to stop cutting before it touches facets A and B to maintain even proportions.
- Pre-Forming: Establish the 5-sided pentagon outline carefully during the 90° girdle cut (Facet 1) to ensure accurate alignment throughout pavilion cutting.
Looking for more free faceting diagrams and precision gemology tutorials? Explore our full collection on Horizon Gems!
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