Question about windowing

[planet_jp]

To determine if/how much a stone is windowed, do you judge the face-up view only, or do you judge from all angles? In other words, is it normal to see through a stone depending on what angle you''re looking at it from?

Thanks.

 

[jeffwhite]

Yes, you would only want to make this judgement by looking directly down into the stone through the table. All stones will "window" when tilted (some more than others). Stones that have a high refractive index (such as diamond) will generally "hold" a tilt more. That is, it will generally take more tilt to cause windowing. Lower refractive index materials, such as quartz and beryl (aquamarine, emeralds, etc.) will window much more easily.

Long story short, it is normal for a stone (even well-cut ones) to be "see through" when viewed from other angles. Hope this helps

 

[planet_jp]

Thank you, Jeff - that totally answered my question. Now, how about extinction. I was told that there will always be some extinction in a colored stone. Is that true? And if so, when does it become too much? Is it just a matter of personal opinion, or is there some objective measurement?

Janet

 

[colormyworld]

Yes it is true that all stones wil show some extinction. There are some exceptions though. Think Kashmir sapphires. These have fine inclusions that fill in the dark areas with color. I have also seen some spinels that have this effect.


Cloudy days and fluorescent lights minimize extinction. Single point light sources like incandescent bulbs will cause a stone to show more extinction.

Lighter colored and brighter colored stones seem to also show less extinction.