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.
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…
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.
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 …
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…
#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