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Crystal inclusion - how to tell if it's really a crystal or

thecat

Brilliant_Rock
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non surfacing reaching feather? For educational purpose. Thank you :))
 
Re: Crystal inclusion - how to tell if it's really a crystal

thecat|1438963694|3912179 said:
non surfacing reaching feather? For educational purpose. Thank you :))
In general a feather will be planar (two dimensional) in nature; much more visible when viewed from a position perpendicular to the feather's plane and almost invisible when line of sight is parallel to the plane. A crystal is typically more three dimensional in nature. It is often necessary to use much higher magnification than the 10X used to grade clarity, in order to determine the exact nature of an inclusion. Even then it takes a grader with a lot of experience to make fine distinctions. Usually it is not necessary to get to that level of detail in order to make a grading call. Of course researchers live for making such distinctions and sleuthing out the exact nature of the minerals trapped inside diamonds.
 
Re: Crystal inclusion - how to tell if it's really a crystal

thecat|1438963694|3912179 said:
non surfacing reaching feather? For educational purpose. Thank you :))

Are you talking about looking at the paper or at the diamond?

Wink
 
Re: Crystal inclusion - how to tell if it's really a crystal

Wink|1438981292|3912304 said:
thecat|1438963694|3912179 said:
non surfacing reaching feather? For educational purpose. Thank you :))

Are you talking about looking at the paper or at the diamond?

Wink

Looking at the diamond. I was as surprised as everyone to learn that GIA calls a non surfacing reaching feather a crystal. So now I'm wondering if one sees a crystal on the cert and it looks white from photos/videos, is it a crystal or feather. Of course, there's no durability issue. But if one sticks around PS long after one's purchase, then we are most likely curious about all things diamond and wish to learn. I must admit that I'm mostly lost when the experts get into technical discussion but I could follow the feather/crystal discussion with no problem at all ;)) So I hope to learn more though I doubt that's useful knowledge when helping newbies select a diamond. :rodent:
 
Re: Crystal inclusion - how to tell if it's really a crystal

Texas Leaguer|1438975834|3912262 said:
thecat|1438963694|3912179 said:
non surfacing reaching feather? For educational purpose. Thank you :))
In general a feather will be planar (two dimensional) in nature; much more visible when viewed from a position perpendicular to the feather's plane and almost invisible when line of sight is parallel to the plane. A crystal is typically more three dimensional in nature. It is often necessary to use much higher magnification than the 10X used to grade clarity, in order to determine the exact nature of an inclusion. Even then it takes a grader with a lot of experience to make fine distinctions. Usually it is not necessary to get to that level of detail in order to make a grading call. Of course researchers live for making such distinctions and sleuthing out the exact nature of the minerals trapped inside diamonds.


Thanks, TL :)) I tried watching videos with your description but am not yet successful at distinguishing between trapped feather or true crystal. Actually I can tell a crystal if it's larger, but it's harder to tell if a small crystal is a feather or crystal. How many x magnification is needed to tell from photos? Impossible, right? Since photos are only 2D. And I think you hit the nail on the head with the bolded statement though I'm no researcher, just a diamond enthusiast ;))
 
Re: Crystal inclusion - how to tell if it's really a crystal

Get yourself a good loupe and then learn how to use a lamp shade to create a simulated dark field illumination area and then just spend a lot of time looking at inclusions. Better yet, find someone with a dark field microscope who will let you play for a while with it.

It is a LOT of fun.

Resa, my wife, used to tell our friends that when ever she did not know where I was she would go into the room that I used as my gem lab and there I would be opening up my gem papers and looking at the gems. We were still students at GIA and I only owned thirty or forty gems then, but I knew them well. I had an early color change garnet, one of the ones that were not supposed to exist being as how they were singly refractive. They insisted on existing anyway

I had a super 2.68 ct tsavorite garmet, deep rich green, sparkle like no emerald could ever emulate and a fantastic cut. I paid six or seven hundred for it back then, a fortune to a former Marine who only had been making a little over $500 a month and was now dependent on the money that could be made buying and selling gems while taking gemology classes at GIA. It would be years before I sold that gem, and I still regret that I ever did so.

For a few days I had an incredible star ruby that was totally transparent, with a sharp star. It had a bright red color to catch your eye and make your heart beat fast, or miss a beat depending on the light that hit the gem when you opened the paper. It was $7,000 and it might as well have been a million, as I had no where near that kind of money. I spent many hours lost in its beauty, gazing into its depths and wishing it could be mine. I have looked long and hard, but have never ever seen or heard of such a gem again, and the price would be hundreds of thousands of dollars today, still beyond my reach, but I would love to see such a gem again, just for the sheer joy of doing so.

I have still the magnificent benitoite I bought from a vendor who came to the GIA premises. We went to a little restaurant next door so that he would not get in trouble for dealing with one of the students on the GIA campus. That gem my wife owns, it is not, never has been, and never will be for sale so long as either of us lives.

There was a "smokey opal" with grayish body color and flashing layers of fire as if it had a diode embedded inside the stone. I sold that to my cousin and made a ring for his wife over thirty years ago. She makes a point of wearing it at least twice a year when she knows I will be in the same room with her and telling me it is her favorite ring and the nicest opal she has ever seen. It is still the most unusual opal I have ever seen, fire like a black but the body color is gray, not black.

Oops, sorry, rambling again. Get a loupe, play and learn and enjoy the internal world of your gem. It will reward you with hours of quiet contemplation and it will bring you more piece that you could ever imagine.

Wink
 
Re: Crystal inclusion - how to tell if it's really a crystal

Wink, thanks for your sharing. :)) It's wonderful to have a job that fascinates you at the same time :appl:
 
Re: Crystal inclusion - how to tell if it's really a crystal

thecat|1438963694|3912179 said:
non surfacing reaching feather? For educational purpose. Thank you :))


The info from Bryan and Wink is great stuff. What you are seeing is likely, in fact, a "non surface reaching feather" ...or is it? By literal definition, GIA has defined a feather as "a separation or break that reaches the surface..." In practice, however, this is not always the case. It can vary from grader to grader and lab to lab. I'm curious, Bryan and Wink, how often do you come across an inclusion called a feather that does not break the surface?
 
Re: Crystal inclusion - how to tell if it's really a crystal

Wonder if now we hear this definition of a GIA feather, if the other labs have the same definition. Lots of us have been here for years and I have never seen longtime jewellers like Wink or GOG say this nor appraisers like Denver appraiser or Oldminer. Unless the graders at AGS, HRD etc have trained with GIA how would they know unless they read the definition in GIA's literature or the GIA Diamond dictionary.

Wonder if this feather being dangerous is just on this board too as all jewellers seem to say it is of no consequence unless in an I2 or so which most would not buy with long term in mind. Sometimes may be said to get buyers to spend more on higher grade diamonds or repeated by people without gemological training who think they are doing good. Sometimes just opinions. GIA does not warn against feathers as far as I have seen. Has anyone seen that anywhere from GIA?

I notice on this board sometimes that what we thought was written in stone was not true at all. e.g. when AGS ideal cut got downgraded to AGS1 for some diamonds and was replaced by a different AGS ideal cut.

Question is - is it only AGS which calls ALL breaks feathers but GIA only names surface breaking ones feathers and other internal breaks are named crystals as the GIA grader meant to say GIA did?
 
Re: Crystal inclusion - how to tell if it's really a crystal

Diamond_Hawk|1439171580|3912840 said:
thecat|1438963694|3912179 said:
non surfacing reaching feather? For educational purpose. Thank you :))


The info from Bryan and Wink is great stuff. What you are seeing is likely, in fact, a "non surface reaching feather" ...or is it? By literal definition, GIA has defined a feather as "a separation or break that reaches the surface..." In practice, however, this is not always the case. It can vary from grader to grader and lab to lab. I'm curious, Bryan and Wink, how often do you come across an inclusion called a feather that does not break the surface?
Hawk,
I think you are right, there are some fine grading calls that vary from grader to grader and lab to lab. Lab grading handbooks also change slightly over time with slightly different terminology or emphasis sometimes introduced. In my experience most of the feathers I have seen break the surface, although I know that it is possible they can be in a "healed" state, either by natural processes or HTHP.

To Pyamid's point I don't think there is much of an issue with durability in rounds (or ovals/cushions) until you get into the imperfect range. Pointed stones are another matter. Points are more vulnerable to begin with. A feather very close to a point can add to that vulnerability and should undergo greater scrutiny.
 
Re: Crystal inclusion - how to tell if it's really a crystal

Bryan when you say most feathers you have seen break the surface, is that the same as what people call an open feather or is that something different again?
 
Re: Crystal inclusion - how to tell if it's really a crystal

Pyramid|1439336984|3913521 said:
Bryan when you say most feathers you have seen break the surface, is that the same as what people call an open feather or is that something different again?
It's often very difficult to see, especially in a small feather, but if you mirror the facet you will usually see a very fine straight line where the feather reaches the surface. They are usually not "open" in the sense that you can see any air space. It is possible that the feather is completely enclosed within the diamond (healed), in which case the polish could be a perfect mirror on the surface of the facet indicating that the feather is not surface reaching.

I have never been a lab grader, so those folks have more experience in actually distinguishing fine details like this. In my normal practice what matters is usually on a slightly broader scale. There are some people with lab experience who might come in an give their perspective on this. 30yearsofdiamonds comes to mind.
 
Re: Crystal inclusion - how to tell if it's really a crystal

Thanks Bryan.
 
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