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Turquoise Grading Part Three


In our final video for our January turquoise grading month Mike looks at some very high grade dark web turquoise from three different mines and grades them using the Turquoise Grading Rules based upon the Robert's Ryan rules for turquoise grading to determine an R2 alpha/numeric grade. Try grading these yourself to see how your grades compare understanding that an actual grade may not be assigned from a photo.




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Erich Raudebaugh
Erich Raudebaugh
21 janv. 2022

Hi Mike, in the video or at least on my screen (which has pretty good color), the color of all of these stones looks almost identical. I wonder if there's any value in having some kind of pantone index color or other reference color by which to help judge turquoise color. I know it's a little subjective, and some of the blues seem to have added depth, maybe due to silica content (the very best Bisbee blue does this, at least for some of my gem grade stones).


Any thoughts?

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mrmryan2
mrmryan2
21 janv. 2022
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You have identified the major weakness of this exercise. Turquoise may not be graded by a photo and the subtle differences in the different mines are lost in the video. For the Turquoise Grading Rules (TGR) to gain acceptance extensive guidelines must be developed. I have started these in the article on grading but they need to be expanded. Your suggestion of a color index is excellent perhaps with examples of different turquoise colors. I am working on Turquoise in America Part Three 1990-2020. When that comes out I may try to work more on the guidelines. Your recommendations are welcome.

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