Sunstone Multi-color, 18 cwt

Hello Ger,

How sure are you that this is a sunstone? I''ve never seen a sunstone with those colors before, rather it looks at first glance like an andalusite or perhaps some kind of "sunset" tourmaline. (If it were it an andalusite it would be huge for that species, and if pretty clean would be rather valuable)

Regardless, yes, any stone can be recut to eliminate a window, but the question always is at what loss of weight and/or diameter. Also since you only see the window at some angles you may have a stone that is already pretty well cut. Each species of gem has a range of "tilt brilliance" when cut to proper proportions. The higher the RI (refractive index) of the gem the more you can tilt it without the gem windowing. So for example take a perfectly cut sapphire and compare it to a perfectly cut quartz. As quartz has a lower RI, it will window when tilted just a few degrees whereas the sapphire has to be tilted substantially in order to window. My point is, that recutting may diminish the windowing but won''t eliminate it at all angles of view.

Barbara

Hi Barbara,

I got this at auction as a Labradorite. It is different from the greens I''ve seen being sold as Labradorite. I have seen some Sunstones in a similar color with the red schiller (I think the red lines might be schiller?). This is extremely difficult for me to capture accurately with the camera. I think the photo of the back shows the colors the best, a kind of lime-olive green with hints of a more blue-green at one end, and those fine lines of red which flash at different angles, and brighten a bit with change of light source.

I tested and got a SG of 2.681, and a RI of 1.550-1.555 (I am not very good at RI''s) With a dichroscope I got 4 colors: yellow-green, blue-green, yellow, and either clear or gray. The SG and RI agree for Labradorite according to Shumann, but he says that there is no pleochroism! (I have the Schumann 1984 edition, and did not know if it was worth buying the newer one??). Sorry I did not have these facts earlier...I am still practicing with all of these "tools."

Anyway, take another look at photo of the back showing the coloring: You can see some of the red threading on the far left. It  is harder to show in the deeper locations, where most of it runs parallel or at a slight angle to the face.


Thanks so much for taking time to answer, and particularly to explain about the windowing. I did not understand how the RI related to this!

Many thanks,
Ger

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18 cwt back lite 1.jpg (31.66 KiB) Viewed 55 times

Date: 9/29/2006 4:17:28 AM
Author: ger100
Hi Barbara,


I got this at auction as a Labradorite. It is different from the greens I''ve seen being sold as Labradorite. I have seen some Sunstones in a similar color with the red schiller (I think the red lines might be schiller?). This is extremely difficult for me to capture accurately with the camera. I think the photo of the back shows the colors the best, a kind of lime-olive green with hints of a more blue-green at one end, and those fine lines of red which flash at different angles, and brighten a bit with change of light source.
Anyway, take another look at photo of the back showing the coloring: You can see some of the red threading on the far left. It is harder to show in the deeper locations, where most of it runs parallel or at a slight angle to the face.
Thanks so much for taking time to answer, and particularly to explain about the windowing. I did not understand how the RI related to this!

From that angle it looks much more like sunstone and your description of the streaks that flash are dead on.