Aquarmarooned!

[VapidLapid]

I recently received this 10.4 carat aqua rough from mozambique. I have been looking at it trying to decide the best orientation for color and the best orientation for size, in avoiding a small, yet shallow, surface breaking feather. There is also some silk that will be unavoidable no mater what, so best color is the primary consideration. The rough has none of the hexagonal crystal surfaces intact, so determining the c axis I was hoping could be guided by color. In the hand the stone has very good color. Outside it was extremely very good color as we had blue sky today. The color is evenly distributed with no zoning. I expect that looking down the c-axis, and looking up the c-axis are the same. I found an orientation where the color was significantly better. I turned the stone around to look backward along the same line and the color was gone! I went back to the original sight and the color was there just as it was. Then I noticed also that rotating the crystal around that same axis, the color disappeared around the 90 degrees, and returned at the 180. No games with polarizers or anything, no change in illumination.

 

[VapidLapid]

now while writing this and preparing the photos, I have discovered another related anomoly. While the color disappeared when the crystal was viewed backward up the presumably c-axis, again when turned 90 degrees it returned, but on the opposite presumptive A/B axis than form the front!

 

[minousbijoux]

It almost looks like sea glass, or should I see "c" glass? It is a very large, very pretty pastel blue

I have faith that you will figure it out when you cut it...

 

[chrono]

Very interesting and highlights one of the very important considerations of the process of faceting - deciding the cut orientation while working around inclusions, preserving weight and more. Alas, I am no lapidary so I'll leave it to the regular lapidaries who post here to share their thoughts and experiences.

 

[Kismet]

That is so neat! Will you facet it or cab it?

 

[VapidLapid]

It seems this phenomenon only occurs when the stone is back-lit by my computer, regardless of the distance between them, and oddly, regardless of the color shown on the screen. I am gonna guess that the aqua is, to some extent, filtering out the red and green pixels, while allowing the blue to shine through on the c-axis. The front/back 90º rotation anomaly I think must be caused by a streching of pixel proportions passing through the stone.

Out in the real world it was quite fine from all sides. These three are iphone pics

 

[FinewaterGems]

You've discovered that a computer monitor emits plane polarized light, which can be used to view pleochroism. Works on a smartphone screen too!

 

[chrono]

Awesome discovery!

 

[bobsiv]

This is why I love looking at my tanzanites in front of a computer screen. Neat effect.

 

[iLander]

That's awesome, VL! How cool is that?!

Every time you start a topic, I learn something new.

(please give us an update about your SO, sometime, VL. I keep sending dust for her . . . )

 

[pregcurious]

Thanks for teaching us VL.

 

[0-0-0]

I think it's fun how colored stones show off the intricacies of lighting. I would have paid a lot more attention in physics class if my teachers taught optics with colored stones.

What are your plans for the piece? It has such nice color outdoors!