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Turquoise Grading


Ever wish there were a way to grade your turquoise? In this video Mike demonstrates the R2 rules of turquoise grading which were explained in a previous Blog article. Follow along as Mike grades various quality of stones all from Bisbee. Then follow the rules to grade these stones your self and enter your results in the comment section.



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Clint Beach
Clint Beach
Jan 11, 2022

I think this was a great selection of variety to do this exercise. When grading these cabs, I copied your hardness scores. In my opinion, #5 is the preeminent stone, worthy of GG, receiving a significantly higher (perfect) color grade, yet lower matrix grade than #6. I think I would need to really practice this system to really hone in on accurate scores that I could be confident in. I'm curious as to if one should grade in parameters of a specific mines known production quality or simply the turquoise world as a whole. Many mines, as you know, simply have not produced GG material. For example one may refer to "gem grade #8" while it may be the "best…


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mrmryan2
mrmryan2
Jan 11, 2022
Replying to

Thank you for your well thought out input. Your grades varied greatly at the lower grades but tended to be closer as grade increased. They were consistently higher than the grades assigned by Philip. Here was the variance. 1-20%, 2-25%, 3-20%, 4-15%, 5-2%, and 6-11%. This may largely be attributed to grading from a photo instead of live but also from grader preference and/or bias.

Miners, traders, jewelers and collectors will see stones through the particular lens of their point of view and conflicts of interests may play a role. For instance a miner may have predominately mid grade in inventory and be hesitant about assigning higher grades in order to protect the price of his/her stone. Online most stone,…


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mrmryan2
mrmryan2
Jan 10, 2022

Excluding the high and low scores in a group of grading results is not always necessary unless the outliers are extreme. In most cases the average of all results would work.

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Philip Chambless
Philip Chambless
Jan 10, 2022

I really tried to make the exercise honest.... Like I was doing it for someone else. On Color, my red/green colorblindness is always going to be a factor. although I do see Blue. However, I can not see grey tones in a color.... so I depend on the color jumping out for me. #5 was the only one with color that stood out to me. On hardness/density, I don't consider "shine" as a legitimate determiner and I really couldn't see much "shine" in the photo.... On Matrix, of course #6 is trying to develop but it's not even... And of course I would need to hold it in my hand and look at the matrix with a jeweler's loop …

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mrmryan2
mrmryan2
Jan 10, 2022

Grading may not be made from photos for the reasons you gave and because photos may be manipulated. This exercise is not for the purpose of determining an actual grade but rather in order to test the grading rules to see how different graders may respond. We are all operating under the same limitation of grading from photos (except for me) so there is a common baseline.

From looking at your grades on the web site I see you grade no stone higher than mid grade. In an instance with such wide variance of grading opinion we would need to check the calibration of grading opinion by seeing what the person giving the low grade would consider high grade.

This…

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Philip Chambless
Philip Chambless
Jan 10, 2022
Replying to

Mike, I don't think you should mitigate the extreme highs and lows but would average the total scores. To drop my perceived scores would be invalidating my honest opinion.... Would you always drop the highest and lowest scores?

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Philip Chambless
Philip Chambless
Jan 10, 2022

#1: C 25 X .50=12.5

H/D 25 X .25= 3.125

M 25 X .25=3.125 = 18.75 = NG


#2: C 35 X .625=21.875

H/D 35 X .375=13.125 = 35 = NG


#3: C 40 X .50=20

H/D 40 X .25=10

M 40 X .25=10 = 40 = NG


#4 C 65 X .50=32.5

H/D 65 X .25=16.25

#5 C 80 X .50= 40=10 = 58.75 = MG


#5 C 80X .50= 40

H/D 70 X .25=17.5

M 60 X.25=15 = 72.5 =MG


#6 C 70 X,50=35

H/D 65 X.25=16.25

M 75 X.25=18.75 = 70 = MG


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Replying to

We have very different opinion of these grades. Since what I see as gem grade you consider mid grade I would really like to see an example of what you consider to be the highest grade.

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