Arya Akhavan (USA)

 

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When I started my first experiments into writing faceting diagrams, there was no FacetDiagrams.org, there were almost no Gemology Online faceting diagrams, and most physical copies (ie Vargas, Graham, Van Sant, Long & Steele) were either nearly impossible for a beginner to find, or were out of print. Since my choices were limited and they were hard to find, I decided to create a large number of diagrams, in a wide range of difficulties and styles, that would be available for free and that I'd be willing to help people with. More importantly, I wanted to talk to as many designers as possible, and research as much of the science behind it as possible, to make sure I understood what was going on. The philosophy applies to these designs for sunstone.

 

CONTACT INFO

email: faceting101@gmail.com

 

 

 

OREGON SUNSTONE PLEOCHROISM RECOMMENDATIONS
(by Arya Akhavan)

 

1. For designs with a cone-shaped pavilion, like barions or rounds, colors will mix together a bit, and the color oriented down the Z axis of the stone will be dominant. If two directions show a weak lighter red and one direction shows a dark green, orient the green down the table and you'll get a green stone with a rim of bronze-red. If two directions show a strong red and one shows a strong green, you can still try and orient the green down the Z axis, but you run the risk of much more color mixing and having more of the stone be a muddy bronze-green. If two directions show green and one shows red, orient the strongest green color down the Z axis, because greens are much more rare than reds.
2. For designs with very "flat" square pavilions, like a classic Princess cut or asscher cut, try and orient the pleochroic color axes exactly in the same directions as the flat pavilion facets (ie color A on the 24-72, color B on the 48-96, color C down the Z axis of the stone). This will preserve the colors and prevent them from mixing. For example, think of a trichroic sunstone that has red, light pink pink, and green. If the light pink is oriented down the Z-axis of the stone, it will distribute mostly evenly and get 'overpowered' by the other two colors. If the green is oriented along the X-axis and the red is oriented along the Y-axis, then your finished stone will distinctly show two green zones, two red zones, and a bit of a pinkish tinge towards the culet.
3. For designs with odd symmetry, like triangles and pentagons, pleochroism and orientation become much more complex and difficult to predict. Try to orient a preferred or dominant color "Q" down the C axis, and one other color along the X-axis. This should give you a stone predominantly "Q"-colored, with a fanlike arrangement of another color along the X-axis.
4. For pieces of rough that are strongly dichroic or trichroic, that have a high L/W ratio, you are limited in your design choices AND in your ability to maximize for color. Think about this like one "short" side and two "long" sides, similar to how tourmaline has one "short" side (the C axis) and one "long" side (the A axis). If your piece of sunstone has two different colors for the "long" sides, there will be no good way to prevent color mixing and you should trim your piece in half. If both "long" sides have the same color, then you can use any design that is optimized for closed-C-axis tourmaline.
5. For additional understanding, please see the GIA's article "Pleochroism in Faceted Gems: An Introduction", by Richard Hughes. The article can be found here.

 

• PANA Mine - Geometric Expletive and PANA Mine - Ninja Star:
• These are square with a cone-shaped pavilion. For pieces with one or two strong green colors, orient the strongest green down the Z axis. For pieces with one strong red direction, one strong green direction, and one very pale direction, orient the very pale direction down the C-axis and you should get interesting color separation at the 96-48 and at the 24-72. For pieces with one or two strong red colors and a weak green or other color, orient the strongest red down the Z-axis.
• see diagram5 b     |     see diagram5 b

 

• PANA Mine - Shifting Sands:

• This is a square with a very flat pavilion. Treat this like a Princess cut - if there's one pale direction, and a separate strong red and strong green, orient the pale color down the Z axis, and the green and red directly down the X and Y axes. It'll give the strongest, least-mixing red and green. If there's two strong reds or two strong greens, then orient the strongest down the Z, and the other two axes directly against the X and Y axes.
• see diagram5 b
•  
• PANA Mine - Zero-Point Burst:
• A standard trillion with a cone-shaped pavilion. Treat it mostly like Geometric Expletive and Ninja Star.
• see diagram5 b
•  
• PANA Mine - Rising Eye and PANA Mine - Sunrise Horizon:
• Keeled designs. For Rising Eye, it minimizes whichever color runs in the X direction (ie from 24 to 72). For Sunrise Horizon, whatever color runs in the X direction will stay separate, but will show up boldly along the 24-72 ends of the stone. Make sure that the color that runs in the Z-direction and the color that runs in the Y direction are the same color, otherwise you'll get bad color mixing for both of these. If you have three colors, try and orient the stone so that the strongest preferred color runs in the Z direction, the most "different" color runs in the X direction, and the palest least-dominant color runs in the Y direction.
• see diagram5 b     |     see diagram5 b
•  
• PANA Mine - Sunset Bell:
• A keeled design. Orient similar to Rising Eye and Sunrise Horizon, but don't forget that the keel on this design runs along the Y-axis and not the X-axis. So, when you're orienting this design, make sure that you rotate it 90 degrees so that the orientation tips match the tips for Rising Eye and Sunrise Horizon. Your most different color should be oriented along the Y-axis, and as you tilt the stone forwards and backwards it should highlight this other color.
• see diagram5 b
•  
• PANA Mine - Sparkling Well:
• A round-ish design, but with an octagonal-ish pavilion. Treat this more like Geometric Expletive and Ninja Star, but the orientation principles of Princess-style pavilions will also come into play. If the rough is trichroic, orient the palest color down the Z and two strong colors along the X and Y, and you should get an interesting effect where both of the strong colors show through with only a little bit of mixing.
• see diagram5 b