GIA color grading

[Richard Sherwood]

Date: 1/18/2005 9:36:54 AM
Author: johnnya

having recently trained with the gia, i can assure you that colour grading is unrelated to the presence or absence of long or short wave uv light.

Can you explain that statement a little further, Johnny?

Are you saying longwave fluorescence has no effect on body color, or are you saying that you used filtered lighting, or bulbs with little or no UV?

I'm trying to figure out the basis for your confident statement.

 

[perry]

Johnnya:

I believe you are misquoting the statistics on statistics...

While it is true that most of the time common folk do not apply proper statistical methods, and therefore present a wrong statistical conclusion (and I will accept that studies have found that to be aproximately 72% of times that statitical based claims are made). It is also true that when the right statistical method is applied to the problem - that the statistical answer is in fact true.

Thus, it is a false statement to claim that 72% of stistics is wrong. It would be more accuarte to claim that people missapply statistics 72% of the time.

I will point out to the statistical novices here that most people usuallly only know simple ratio statistics, or odds, or of the "standard normal statistical distribution" (the one on your calculator). What most of you do not know is that there are a number of other common statistical distributions, and that even the standard normal distribution requires a minimum number of data point to be valid ( I could look it up, but I default to a minimum of 30 data points for a standard normal analysis). It is the job of the statistitian to make sure that you are using the right statistical distribution for your problem and ensure that you have enough data points for the analysis to be valid (and there are further requirments depending on how valid (accurate) you want the answer to be). Since most people do not know this, they missapply statistics quite often. Scientist and Engineers typically have a real good understanding of statistics as it is required for their work (and in some colleges they esentially have a minor in statistics by the time they graduate as a Scientist or Engineer).

As someone who purports to have a degree in statistical analysis - I find it very disturbing that first you would claim that statistics are wrong most of the time and then blindly claim that the statistics cited are probably wrong without checking out the study that produced them to determine if the statistical method used was apporpriate for the problem.

I have read the GIA study that those numbers came from, and in my opinion the statistics reported for the number of diamonds with fluoresence are correct (and I have seen similar numbers from other sources: +/- a few %).

However, I will admit that I view the situation as presented by Marty is not in my opinon totally correct. Diamonds with faint fluoresence will not color shift enough enough to affect grading.

Other reports I have read indicates that approximately 1/3 of the fluoresence (aproximately 10% of the total diamond population) has enough fluoresence to color shift 1 color grade in the presence of bright normal sunlight. An extreemly small percentage (perhaps 1/10 of 1% of the total diamond poplulation: 1 out of a 1000) will color shift 2 grades.

I would also like to point out that 500 years ago: The greatest minds, and even the common people, knew that the earth was round. In fact, several thousand years ago a fairly accurate calcualtion of the diameter of the earth was made.

The "Flat Earth" story was actually invented in the 1800's when the public school systems were starting. The authors of American history wanted to present that Columbus was a hero, and it would not do to tell american children that he was horribly wrong about his calcualtions on the diameter of the earth (Columbus calculated that the earth was about 1/2 of its diameter). The reason Columbus could not get funding from all the other kindoms was that everyone else dismissed his calculations as wrong. Good thing there was land in the middle of the great sea to the west, or he and his crew would have starved...

All of the books and nautical information of the last sevearl thousand years - up to the 1800's talked about the round earth (it is even in the Bible). The navigation instruments that Columbus used was also based on a round earth. Do you really think that the sailors did not quickly figure out that the reason they could not see land was because of the curvature of the earth. I suggest you spend some time at sea: it is actually rather obvious...

Perry

 

[johnnya]

to perry and all the others: the quote about 72% of statistics was IRONIC. it is supposed to make you reflact on the nature of numbers, and the validity of "statistics" quoted that do not reference sources and are of questionable validity.

as for the 35% number. this is an estimate, followed by the word "potentially". do we know that this is accurate? if so, what %age of the 35% will actually change? what %age will change colour? what %age of the %age that change colour will change colour due to fluorescence? what %age of the %age that change colour will change colour due to viewer error, normal variances in human input into absolute judgements such as colour? has this numbert ever been tested? what %age will change simply due to different standards and more rigourous enforcement applied nowadays? i would not expect a stone graded 50years ago to grade the same today, a point that the round world/flat world comment was intended to illustrate.

as for my certainty in the negattory effects of uv on colour, if i''m not mistaken, the same gia article on fluorescence determinded that. regardless, that article is some seven or eight years old. recently, ie in the last few years, the gia updated all of its diamond grading courses in the last three years, and while i''m not going to go into propriety information, i can assure you that today''s training takes full account of fluorescence.

and i''m sure that galileo would differ with perry on his timeline of flat-worldism!

 

[denverappraiser]

Date: 1/19/2005 6:28:31 AM
Author: johnnya

..., and while i''m not going to go into propriety information, i can assure you that today''s training takes full account of fluorescence.

Johnnya,

Thanks for participating in the forum.

Material taught to students GIA''s their classrooms is hardly proprietary. On the contrary, they are making a deliberate effort to propagate their grading standards and procedures as widely as possible and the classes were created for exactly this purpose. How could it be inappropriate for you to share this information? I can''t imagine that they would consider the content of their curriculum to be proprietary although their specific method for presenting it involves some copyrighted material.

Neil Beaty
GG(GIA) ISA NAJA
Independent Appraisals in Denver

 

[perry]

Johnnya:

Galileo would not object to the round earth concept at all. Much of his work as it related to astronomy and gravity was based on a round earth.

Mariners who were sailing up and down the African and West European/NW European coast had been using instruments to measure their latitide since in the 1300''s. Even earlier latitude instruments existed in the India ocean. The instuments that existed in Columbus''s days were accurate to about 1% latitude. However, while Columbus knew of them, and took them with him on his voyages, he did not know how to really use the instruments because he had spent his carrear sailing the Meditrainian Sea - where the latitude is mostly the same and the Meditrainian mariners did not use those instruments (why measure something that did not change much for what you were doing). The end result is that Columbus recorded the wrong readings from his latitude measuring devices in his logs on his trips to america, and noted that they were almost certainly wrong (and lost faith in the instruments). In the case of the one instrument, which also had a tangent table on it, assuming that Columbus recorded the tangent numbers - the resultant latitude numbers would have been right for his location.

I suggest that you take some time to check the facts behind these and other items before replying.

As far as your questions related to probably effects of Fluoresence on diamonds and color grading. I provided the information above based on all of my reseach into the subject. I have been waiting for some independent information from GIA before commenting on what changes GIA may have actally made (and I have someone poking arround - as time permits - on the issue). However, the affects of fluroesences on color grading is well know. The changes, if any, by GIA is covered in secracy as GIA has not wanted to directly answer questions on it.

I do have to say, Johnnya, that I would welcome further insite on the issue: However, you need to come up with more than a statement that GIA has fully accounted for it (like details of exactly what the GIA is using for todays color grading vs several years ago) - and you have to come accross as credible.

Perry

 

[johnnya]

it is indeed propriety information. all who wish to know it might consider enrolling in their updated class.

as for the flatworlders, columbus sailed after galileo''s time. he was tortured for his "heretical" belief that the world was round.

 

[windowshopper]

Date: 1/19/2005 9:20:43 AM
Author: johnnya


it is indeed propriety information. all who wish to know it might consider enrolling in their updated class.

as for the flatworlders, columbus sailed after galileo''s time. he was tortured for his ''heretical'' belief that the world was round.

heretical or not he clearly "knew" it was round--thanks Perry

Read Sails of Hope if you want a really interesting perspective on Columbus

 

[Richard Sherwood]

Date: 1/19/2005 6:28:31 AM
Author: johnnya

and while i''m not going to go into propriety information, i can assure you that today''s training takes full account of fluorescence.

Okay, I get it. You don''t know.

That''s okay.

It''s nice to have you aboard. Keep posting. This crowd is pretty sophisticated, and can be tough at times, but it''s amazing how much you''ll pick up. I know I have.

 

[windowshopper]

Date: 1/19/2005 10

6:20 AM
Author: Richard Sherwood

Date: 1/19/2005 6:28:31 AM
Author: johnnya

and while i''m not going to go into propriety information, i can assure you that today''s training takes full account of fluorescence.

Okay, I get it. You don''t know.

That''s okay.

It''s nice to have you aboard. Keep posting. This crowd is pretty sophisticated, and can be tough at times, but it''s amazing how much you''ll pick up. I know I have.

 

[Garry H (Cut Nut)]

Yes, Welcome Johnny.

Sorry about the initiaion proceedure. It is easy to assume that this board is just a bunch of consumers who know didly squat.
It is interesting that there are many lurkers from esteemed gem organisations who can not post. but they read

 

[windowshopper]

Date: 1/19/2005 5:53:52 PM
Author: Garry H (Cut Nut)
Yes, Welcome Johnny.

Sorry about the initiaion proceedure. It is easy to assume that this board is just a bunch of consumers who know didly squat.
It is interesting that there are many lurkers from esteemed gem organisations who can not post. but they read

ruh-ro ! big brother is watching...

 

[canuk-gal]

Date: 1/18/2005 8:19:23 PM
Author: perry

It is also true that when the right statistical method is applied to the problem - that the statistical answer is in fact true.

Perry

HI:

Interesting. But just to clarify, statistical inferences are based on "incomplete information" (aka entire populations are so often not available), hence there is always a risk of making an error....for example type 1 and type 11 errors....

And b/c there is "talk" of "armchair experts" and "shills" posting on threads, please do not take my word as gospel; there are hundreds of books, thousands of chapters and millions of words written on this and related subjects...................

Sorry to bug. Back to your regular programming.

cheers--Sharon

 

[perry]

Johnnya:

This is getting ridiculous...

Galileo was not branded a heritic and restricted from publication because the earth was round. The roman church knew that...

He was restricted because he stated that the Copernican model of the solar system was right - and the earth rotated arround the sun. Copernicus was the person who first seriously proposed that the earth revolved arround the sun, instead of the accepted model where - where the universe rotated arround the earth. Galileo was the first person to gather scientific data to demonstrate that the planets rotated arround the sun, based on use of the telescope he invented.

Also, just to clear the air on what Copernicus knew... The english translation of the title of his paper was: On the revolutions of the celesrial spheres Published in 1543.

Everyone knew the earth was round, common knowledge recorded in vertually every book that has survived for thousands of years, including the writings and books from about the first 100 years of america.

However, it was belived that the earth was the center of the universe, and challanging that invoked the wrath of the roman church. Thus Galileo was prosecuted for heresy.

As stated in my post above: "American" Flat earth stories were invented to make Christopher Columbus look heroic, and not stupid and lucky. Most of the rest of the world (especially Euorpe) is surprised to hear from americans that we generally belive that the people in the 1600's thought the earth was flat and that Christopher braved grave danger becaruse he would sail off of the edge of the world (laughter is common, if they don't think of getting you, help).

Otherwise, welcome to the forum. Please do yourself a favor and do a few minutes of research into things before you post.

As far as the "Propriatary" information from GIA. You are right in a fashion. The details are essentially propriatary because the people in the know at GIA do not want to talk about the issue. There is nothing in their course materials that is propriatary.


Canuk-gal: Hey, glad to meet someone else who knows statistics. you are of course right, and I won't bore the forum with the discussion on confidence intervals...