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Blue sapphires with no half/half extinction?

lominoblue

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Let's settle the half/half extinction debate once and for all. Is there really such a thing as a sapphire without it? Let's prove it on this thread!

I've been following the postings on the colored stones forum and I've seen quite a bit of discussion over half/half extinction. I'm looking around for a sapphire and hoping to find one that does not have it. However, since it seems to be hotly contested whether there really is such a thing as a sapphire with no half/half extinction I thought I could ask PSers to show there blue sapphires that have no half/half. I'm hopeful I can learn something by looking at the cuts and, more importantly, convince myself that there is such as a thing as a blue sapphire with no half/half.

Since it is easy to take a still shot of a blue sapphire under just the right lighting conditions so that it does not show half/half, I was wondering if we could keep the handshots and preferably videos rotating the sapphire 360 degrees to indoor lighting conditions where there is a point light source (e.g., lamp or ceiling light) rather than a really bright day outside where half/half is less likely to occur.
 

ChrisA222

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Concave cuts!
 

FrekeChild

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Half and half is a result of the cut/shape, not the variety of stone. If a stone is elongated, odds are pretty good that it'll have half and half extinction.

Lavender radiant sapphire and round tsavorite

Round sapphire and spinel.

All precision cut, radiant and lower blue stone by Gene, tsav and upper blue stone by Barry.

img_0433.jpg

_3067.jpg
 

MakingTheGrade

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I have a lavender sapphire supernova oval with no half an half extinction. And a blue trillion sapphire that doesn't have it due to the shape.
 

chrono

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It is a function of cut, not gem type. To lessen the chance of seeing this, stick with rounds. Basically, anything with an elongated shape risks this, be it an oval or rectangular shaped stone. The only exception I've seen so far are concave cuts and supernova ovals.

blue_light.png
 

LD

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This is exactly why I started a thread a while ago asking people to stop using the term half/half as it's incredibly misleading! :nono:

There are many many many many many sapphires (and other gemstones) that DO NOT exhibit this. As others have said, this is a function of cut not gem species. Half/half extinction is really only seen in a very small proportion of gemstones.

Extinction to varying degrees is seen in ALL gemstones and in ALL cuts because it's just like life - it has light and shade! If you search this forum you'll see loads of sapphires that don't exhibit it but do have some extinction which is ABSOLUTELY NORMAL!

Sorry, I'll get off my soapbox now but this is a pet peeve of mine! :-o
 

lominoblue

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I was happy to see that some people responded! Thanks to everyone!

In looking at many prior postings I saw many point out the half/half on oval cut blue sapphires as a drawback or criticism and mentioned that there existed such sapphires without half/half, but it was never clear if it meant that there existed oval sapphires without the half/half (with the exception of concave cut). It seems now that when people say there are sapphires without half/half they are referring to non-oval cuts or special cuts...

From above it seems that sapphires without the half/half tend to be "round shape" or "trilliant shape" or oval with "concave cut" or "supernova cut."

I think this is an important clarification for me and the newbies. Most blue sapphires out there are oval and of brilliant step cut. So it drives people crazy when one says that there are sapphires without half/half but don't specify that it has to be something other than an oval or a special cut of oval "concave" or "supernova."

Given the new info, some people would prefer the traditional oval cut with half/half over a concave cut oval or a different shape, such as a round.

Chrono > Thanks for showing the round sapphire with a single point light source.
LD > Yes half/half seems to be an unfair and misleading terminology especially when used to criticize an oval. I have to disagree with my interpretation of your statement that there are many, many, many sapphires that don't have it. My experience has been that the majority of blue sapphires are oval and traditional cut, which means they all have half/half.

What is different about a "supernova" cut over a traditional brilliant step cut?
All this is a mute point if someone *does* have a traditional brilliant step cut oval blue sapphire that shows no half/half in all lighting conditions?
 

chrono

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Take a look at GemFix to see oodles of blue sapphires in ovals without this type of extinction. Ovals do not appeal to me aesthetically which is why I rarely own ovals.
http://www.gemfix.com/sapphire_blue.html
 

lominoblue

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Yup, gemfix seems to have some special cuts.

Is the Barry mentioned in association with supernovas, this guy: http://www.acstones.com/ Seems like it is not easy to find supernova cuts that are greater than 2ct and also saturated blue.

I actually *love* the oval shape. It feels more vintage and unique to me.

By the way, I bet that a round-oval would have less half/half. A true oval with a width:length ratio of 1.3 or greater would probably have more half/half than one with a ratio of 1.1-1.2.

I really think people should mention supernova cut more often. I've heard of concave cut, but never heard supernova cut mentioned when talking about half/half.

Chrono|1358266928|3356020 said:
Take a look at GemFix to see oodles of blue sapphires in ovals without this type of extinction. Ovals do not appeal to me aesthetically which is why I rarely own ovals.
http://www.gemfix.com/sapphire_blue.html
 

lominoblue

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I found this useful bit. Too bad supernovas have to be made deeper.

_3074.jpg
 

chrono

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Barry is the lapidary from ACStones.

I do not study the ins and outs of faceting ovals but would like to know the basis for your reasoning that an oval with a ratio greater than 1:1.3 would have a higher chance of this look as compared to a 1:1.2

I own 2 ovals, both being blue spinels that do not show this half look. One is precision cut with a 1:1.23 ratio, the other is non precision cut with a 1:1.28 ratio. Since you asked specifically for blue sapphires, I did not post them.
 

LD

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It is more commonly seen in ovals BUT again I would say that this is NOT the norm. Don't forget, what you see on here is only a tiny proportion of gemstones in the market place!

Here are some of my ovals that don't have it just to prove they exist and none of these are supernovas!!! All are sapphires but as I don't generally like blue sapphires, you'll have to understand that I only have one in blue - all the others are different colours. Only one of the following ovals shows anything near the half half and that's the one in the bracelet to the far right!

sapphire_purple_1.jpg

sapphire_cc_bracelet_1.jpg

sapphire_cc_face_1_1.jpg

sapphire_ceylon__amp__diamond_ring.jpg
 

lominoblue

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Chrono|1358268370|3356054 said:
Barry is the lapidary from ACStones.

I do not study the ins and outs of faceting ovals but would like to know the basis for your reasoning that an oval with a ratio greater than 1:1.3 would have a higher chance of this look as compared to a 1:1.2

I own 2 ovals, both being blue spinels that do not show this half look. One is precision cut with a 1:1.23 ratio, the other is non precision cut with a 1:1.28 ratio. Since you asked specifically for blue sapphires, I did not post them.


My logic for the ratio was that if it is more round than it would behave more like a round.

The blue spinels sound interesting. I don't know if they have a different refractive index to the blue sapphire. But maybe blue spinels are a good alternative if they don't have the half/half as much as blue sapphires. Could you please show them on here with a point light source like you did for your round sapphire? I just know that anyone could take a hand shot to showcase the gem under the best conditions and not showing half/half... so this is a good way to get around that. :)
 

lominoblue

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LD|1358268498|3356057 said:
It is more commonly seen in ovals BUT again I would say that this is NOT the norm. Don't forget, what you see on here is only a tiny proportion of gemstones in the market place!

Here are some of my ovals that don't have it just to prove they exist!!! All are sapphires but as I don't generally like blue sapphires, you'll have to understand that I only have one. The others are different shapes. Only one of the following ovals shows anything near the half half and that's the one in the bracelet to the far right!

You have quite the gorgeous collection.

So I can count at least 4 sapphires in the bracelet that have half/half. Wouldn't you agree? My definition of half/half is half is darker and half is lighter... not half is black and half is light.

As for the other sapphires, are they all the traditional step cuts?

The pink sapphire in ring setting and the blue sapphire in ring look like they do not have half/half. The pink sapphire looks most convincing because of how the ring is set. I don't know if pink sapphires are intrinsically different from blue sapphires. The blue one looks like a professional pic and don't know what is going on, although it does look to have a single point light source. I still wish we could see it under normal everyday conditions.

Unfortunately I'm going to be the devil's advocate and say that a still picture could show any gem without half/half. Of course I believe you. But for real proof to everyone PSers (sorry to be a pain in the butt) it would be necessary to see a point light source like Chrono took under normal real life conditions (non-professional) or a video taken under normal light conditions (except when it is super sunny and bright) where one turns the sapphire 360 degrees. The latter would truly be definitive in my mind. Otherwise, for someone like me who has never seen an oval without half/half... I'm left to believing it is a myth. :( I've looked at many in the past month... not just the ones posted on here by PSers.
 

PrecisionGem

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"Half and Half" has nothing to do with the stone. If anything, and sapphire would be less prone to this than something with lower refractive index such as a citrine.

As stones become longer, you tend to see this more. The "SuperNova" oval design is really nothing special, there are many oval designs that do not exhibit this H&H effect that I prefer over the SuperNova. I cut a rather long 2:1 ratio oval that has full brilliance. Generally I stay away from the oval designs with a keel pavilion, they typically don't perform well.
 

lominoblue

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PrecisionGem|1358269311|3356072 said:
"Half and Half" has nothing to do with the stone. If anything, and sapphire would be less prone to this than something with lower refractive index such as a citrine.

As stones become longer, you tend to see this more. The "SuperNova" oval design is really nothing special, there are many oval designs that do not exhibit this H&H effect that I prefer over the SuperNova. I cut a rather long 2:1 ratio oval that has full brilliance. Generally I stay away from the oval designs with a keel pavilion, they typically don't perform well.

Was the 2:1 oval a "traditonal" step cut or concave cut or other? And had no half/half?

So, in other words, there exist oval blue sapphires with "traditional" step cut that have no half/half? How rare are they?

If not the stone and not the type of cut, then what is the secret to an oval blue sapphire not having the half/half?

What do you mean by keel pavilion does not perform well? (is this in regard to half/half or other)
 

LD

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lominoblue|1358269098|3356069 said:
LD|1358268498|3356057 said:
It is more commonly seen in ovals BUT again I would say that this is NOT the norm. Don't forget, what you see on here is only a tiny proportion of gemstones in the market place!

Here are some of my ovals that don't have it just to prove they exist!!! All are sapphires but as I don't generally like blue sapphires, you'll have to understand that I only have one. The others are different shapes. Only one of the following ovals shows anything near the half half and that's the one in the bracelet to the far right!

You have quite the gorgeous collection.

So I can count at least 4 sapphires in the bracelet that have half/half. Wouldn't you agree? My definition of half/half is half is darker and half is lighter... not half is black and half is light.

As for the other sapphires, are they all the traditional step cuts?

The pink sapphire in ring setting and the blue sapphire in ring look like they do not have half/half. The pink sapphire looks most convincing because of how the ring is set. I don't know if pink sapphires are intrinsically different from blue sapphires. The blue one looks like a professional pic and don't know what is going on, although it does look to have a single point light source. I still wish we could see it under normal everyday conditions.

Unfortunately I'm going to be the devil's advocate and say that a still picture could show any gem without half/half. Of course I believe you. But for real proof to everyone PSers (sorry to be a pain in the butt) it would be necessary to see a point light source like Chrono took under normal real life conditions (non-professional) or a video taken under normal light conditions (except when it is super sunny and bright) where one turns the sapphire 360 degrees. The latter would truly be definitive in my mind. Otherwise, for someone like me who has never seen an oval without half/half... I'm left to believing it is a myth. :( I've looked at many in the past month... not just the ones posted on here by PSers.

All of the photos were taken by ME not a photographer.

The blue oval has a window - no half half. The window is what you're seeing and don't understand.

It seems to me that no matter how many ovals people post you won't believe that half half is not common. You've asked to see photos but then are saying that they're not "real proof" - sorry, but I'm not going to take my gems to a professional photographer just to prove a point! You asked, I told you you were wrong and have shown you photos (some that were taken several years ago which proves I didn't manipulate the photos just for this thread!).

I have no idea what you're seeing when you look at the photo of the bracelet but you're looking at photos of gems at different angles and you're assessing them as having half/half?????!!!! If you look, you'll see that the sapphires have been photographed from all different angles because I couldn't get a close up of them when they're in one line. Believe me when I say that only ONE stone in that bracelet shows anything near the extinction you're referring to. A sapphire is a sapphire is a sapphire - it doesn't matter what colour it is. It is the same material. ALL of the sapphires I've posted are normal step cuts.

I'm sorry but this thread is EXACTLY the reason why all the threads where half/half have been mentioned is so misleading.
 

PrecisionGem

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Here is a spinel cut in a 2:1 ratio oval. No "Half & Half". Spinel and sapphire have RI that are very close.
(Stone is not for sale... )

1154.jpg
 

chrono

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lominoblue|1358269098|3356069 said:
My definition of half/half is half is darker and half is lighter... not half is black and half is light.

I disagree but that is only my opinion - I only consider it as half/half when one side is black and the other is light. If I can still see colour, I don't mind it as much and do not consider it so. Corundum is corundum; it does not matter that one is blue or pink. I have also seen plenty of spinels that show this half/half. Although the picture below does not show a strong light source coming from one side, it clearly shows the rectangular spinel with an obviously very dark half and a light half. The oval spinel does not show this. No picture or colour editing used other than to crop out the background. No hand shading or diffusing the light. Since one stone shows this darkness in this lighting condition, it should be proof enough that the oval doesn't since both are photographed together at almost the same angle. Both are precision cut.

ETA
This isn't a true half/half but comes close.

tale_of_2_spinels.png
 

lominoblue

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LD|1358269747|3356079 said:
lominoblue|1358269098|3356069 said:
LD|1358268498|3356057 said:
It is more commonly seen in ovals BUT again I would say that this is NOT the norm. Don't forget, what you see on here is only a tiny proportion of gemstones in the market place!

Here are some of my ovals that don't have it just to prove they exist!!! All are sapphires but as I don't generally like blue sapphires, you'll have to understand that I only have one. The others are different shapes. Only one of the following ovals shows anything near the half half and that's the one in the bracelet to the far right!

You have quite the gorgeous collection.

So I can count at least 4 sapphires in the bracelet that have half/half. Wouldn't you agree? My definition of half/half is half is darker and half is lighter... not half is black and half is light.

As for the other sapphires, are they all the traditional step cuts?

The pink sapphire in ring setting and the blue sapphire in ring look like they do not have half/half. The pink sapphire looks most convincing because of how the ring is set. I don't know if pink sapphires are intrinsically different from blue sapphires. The blue one looks like a professional pic and don't know what is going on, although it does look to have a single point light source. I still wish we could see it under normal everyday conditions.

Unfortunately I'm going to be the devil's advocate and say that a still picture could show any gem without half/half. Of course I believe you. But for real proof to everyone PSers (sorry to be a pain in the butt) it would be necessary to see a point light source like Chrono took under normal real life conditions (non-professional) or a video taken under normal light conditions (except when it is super sunny and bright) where one turns the sapphire 360 degrees. The latter would truly be definitive in my mind. Otherwise, for someone like me who has never seen an oval without half/half... I'm left to believing it is a myth. :( I've looked at many in the past month... not just the ones posted on here by PSers.

All of the photos were taken by ME not a photographer.

The blue oval has a window - no half half. The window is what you're seeing and don't understand.

It seems to me that no matter how many ovals people post you won't believe that half half is not common. You've asked to see photos but then are saying that they're not "real proof" - sorry, but I'm not going to take my gems to a professional photographer just to prove a point! You asked, I told you you were wrong and have shown you photos (some that were taken several years ago which proves I didn't manipulate the photos just for this thread!).

I have no idea what you're seeing when you look at the photo of the bracelet but you're looking at photos of gems at different angles and you're assessing them as having half/half?????!!!! If you look, you'll see that the sapphires have been photographed from all different angles because I couldn't get a close up of them when they're in one line. Believe me when I say that only ONE stone in that bracelet shows anything near the extinction you're referring to. A sapphire is a sapphire is a sapphire - it doesn't matter what colour it is. It is the same material. ALL of the sapphires I've posted are normal step cuts.

I'm sorry but this thread is EXACTLY the reason why all the threads where half/half have been mentioned is so misleading.

Please do not take my comments to be nothing other than trying to make this the definitive thread that puts the half/half debate over and to eliminate any misleading. I hope you understand.

Also, I was not saying you should take your gems to a professional photographer. Of course not! Quite the contrary, I just wanted a plain simple phone camera picture or video. Pretty easy to do in today's techy world. But I understand if you are busy or cannot.

The bracelet... this is an interesting point. Maybe our definitions of half/half are different. I've attached a pic to illustrate what I mean. Yellow is light and Blue is dark. I've pointed to four sapphires. Your camera is like the eye. So what you are seeing is half/half in different sapphires because of how the light source is hitting them. This is why for a give sapphire with half/half you can take move it so that light hits in a way that shows no half/half and why still photos are not necessarily accurate representations.

2sapphire_cc_bracelet_1.jpg
 

lominoblue

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Chrono|1358270191|3356087 said:
lominoblue|1358269098|3356069 said:
My definition of half/half is half is darker and half is lighter... not half is black and half is light.

I disagree but that is only my opinion - I only consider it as half/half when one side is black and the other is light. If I can still see colour, I don't mind it as much and do not consider it so. Corundum is corundum; it does not matter that one is blue or pink. I have also seen plenty of spinels that show this half/half. Although the picture below does not show a strong light source coming from one side, it clearly shows the rectangular spinel with an obviously very dark half and a light half. The oval spinel does not show this. No picture or colour editing used other than to crop out the background. No hand shading or diffusing the light. Since one stone shows this darkness in this lighting condition, it should be proof enough that the oval doesn't since both are photographed together at almost the same angle. Both are precision cut.

ETA
This isn't a true half/half but comes close.


Excellent proof! So the spinel is a precision cut... do you know what type of cut and who does or did the cut for you?

Any chance you could take a pic from the other camera angle or zoom in on the spinel a little more?

So this is interesting. Our definitions of half/half is different. Of course if half/half is half black and half is light then it is not very common at all! If you use my definition then it is very common!
 

LD

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lominoblue|1358270370|3356089 said:
LD|1358269747|3356079 said:
lominoblue|1358269098|3356069 said:
LD|1358268498|3356057 said:
It is more commonly seen in ovals BUT again I would say that this is NOT the norm. Don't forget, what you see on here is only a tiny proportion of gemstones in the market place!

Here are some of my ovals that don't have it just to prove they exist!!! All are sapphires but as I don't generally like blue sapphires, you'll have to understand that I only have one. The others are different shapes. Only one of the following ovals shows anything near the half half and that's the one in the bracelet to the far right!

You have quite the gorgeous collection.

So I can count at least 4 sapphires in the bracelet that have half/half. Wouldn't you agree? My definition of half/half is half is darker and half is lighter... not half is black and half is light.

As for the other sapphires, are they all the traditional step cuts?

The pink sapphire in ring setting and the blue sapphire in ring look like they do not have half/half. The pink sapphire looks most convincing because of how the ring is set. I don't know if pink sapphires are intrinsically different from blue sapphires. The blue one looks like a professional pic and don't know what is going on, although it does look to have a single point light source. I still wish we could see it under normal everyday conditions.

Unfortunately I'm going to be the devil's advocate and say that a still picture could show any gem without half/half. Of course I believe you. But for real proof to everyone PSers (sorry to be a pain in the butt) it would be necessary to see a point light source like Chrono took under normal real life conditions (non-professional) or a video taken under normal light conditions (except when it is super sunny and bright) where one turns the sapphire 360 degrees. The latter would truly be definitive in my mind. Otherwise, for someone like me who has never seen an oval without half/half... I'm left to believing it is a myth. :( I've looked at many in the past month... not just the ones posted on here by PSers.

All of the photos were taken by ME not a photographer.

The blue oval has a window - no half half. The window is what you're seeing and don't understand.

It seems to me that no matter how many ovals people post you won't believe that half half is not common. You've asked to see photos but then are saying that they're not "real proof" - sorry, but I'm not going to take my gems to a professional photographer just to prove a point! You asked, I told you you were wrong and have shown you photos (some that were taken several years ago which proves I didn't manipulate the photos just for this thread!).

I have no idea what you're seeing when you look at the photo of the bracelet but you're looking at photos of gems at different angles and you're assessing them as having half/half?????!!!! If you look, you'll see that the sapphires have been photographed from all different angles because I couldn't get a close up of them when they're in one line. Believe me when I say that only ONE stone in that bracelet shows anything near the extinction you're referring to. A sapphire is a sapphire is a sapphire - it doesn't matter what colour it is. It is the same material. ALL of the sapphires I've posted are normal step cuts.

I'm sorry but this thread is EXACTLY the reason why all the threads where half/half have been mentioned is so misleading.

Please do not take my comments to be nothing other than trying to make this the definitive thread that puts the half/half debate over and to eliminate any misleading. I hope you understand.

Also, I was not saying you should take your gems to a professional photographer. Of course not! Quite the contrary, I just wanted a plain simple phone camera picture or video. Pretty easy to do in today's techy world. But I understand if you are busy or cannot.

The bracelet... this is an interesting point. Maybe our definitions of half/half are different. I've attached a pic to illustrate what I mean. Yellow is light and Blue is dark. I've pointed to four sapphires. Your camera is like the eye. So what you are seeing is half/half in different sapphires because of how the light source is hitting them. This is why for a give sapphire with half/half you can take move it so that light hits in a way that shows no half/half and why still photos are not necessarily accurate representations.


None of what you've pointed to is what people are referring to as "half/half" in my photo other than the gem I had already identified as being on the far right. If you look at Chrono's post two posts above, you'll see the pink spinel is showing half/half. What you've pointed to in my photos is nothing more than extinction AND in some cases (although actually not in the photos I've posted) may be caused by a bow tie effect. A bow tie is very very different from half/half. You can only assess gems head on - not from one side.

I agree with Chrono's assessment of half/half also.
 

lominoblue

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LD|1358270661|3356095 said:
lominoblue|1358270370|3356089 said:
LD|1358269747|3356079 said:
lominoblue|1358269098|3356069 said:
LD|1358268498|3356057 said:
It is more commonly seen in ovals BUT again I would say that this is NOT the norm. Don't forget, what you see on here is only a tiny proportion of gemstones in the market place!

Here are some of my ovals that don't have it just to prove they exist!!! All are sapphires but as I don't generally like blue sapphires, you'll have to understand that I only have one. The others are different shapes. Only one of the following ovals shows anything near the half half and that's the one in the bracelet to the far right!

You have quite the gorgeous collection.

So I can count at least 4 sapphires in the bracelet that have half/half. Wouldn't you agree? My definition of half/half is half is darker and half is lighter... not half is black and half is light.

As for the other sapphires, are they all the traditional step cuts?

The pink sapphire in ring setting and the blue sapphire in ring look like they do not have half/half. The pink sapphire looks most convincing because of how the ring is set. I don't know if pink sapphires are intrinsically different from blue sapphires. The blue one looks like a professional pic and don't know what is going on, although it does look to have a single point light source. I still wish we could see it under normal everyday conditions.

Unfortunately I'm going to be the devil's advocate and say that a still picture could show any gem without half/half. Of course I believe you. But for real proof to everyone PSers (sorry to be a pain in the butt) it would be necessary to see a point light source like Chrono took under normal real life conditions (non-professional) or a video taken under normal light conditions (except when it is super sunny and bright) where one turns the sapphire 360 degrees. The latter would truly be definitive in my mind. Otherwise, for someone like me who has never seen an oval without half/half... I'm left to believing it is a myth. :( I've looked at many in the past month... not just the ones posted on here by PSers.

All of the photos were taken by ME not a photographer.

The blue oval has a window - no half half. The window is what you're seeing and don't understand.

It seems to me that no matter how many ovals people post you won't believe that half half is not common. You've asked to see photos but then are saying that they're not "real proof" - sorry, but I'm not going to take my gems to a professional photographer just to prove a point! You asked, I told you you were wrong and have shown you photos (some that were taken several years ago which proves I didn't manipulate the photos just for this thread!).

I have no idea what you're seeing when you look at the photo of the bracelet but you're looking at photos of gems at different angles and you're assessing them as having half/half?????!!!! If you look, you'll see that the sapphires have been photographed from all different angles because I couldn't get a close up of them when they're in one line. Believe me when I say that only ONE stone in that bracelet shows anything near the extinction you're referring to. A sapphire is a sapphire is a sapphire - it doesn't matter what colour it is. It is the same material. ALL of the sapphires I've posted are normal step cuts.

I'm sorry but this thread is EXACTLY the reason why all the threads where half/half have been mentioned is so misleading.

Please do not take my comments to be nothing other than trying to make this the definitive thread that puts the half/half debate over and to eliminate any misleading. I hope you understand.

Also, I was not saying you should take your gems to a professional photographer. Of course not! Quite the contrary, I just wanted a plain simple phone camera picture or video. Pretty easy to do in today's techy world. But I understand if you are busy or cannot.

The bracelet... this is an interesting point. Maybe our definitions of half/half are different. I've attached a pic to illustrate what I mean. Yellow is light and Blue is dark. I've pointed to four sapphires. Your camera is like the eye. So what you are seeing is half/half in different sapphires because of how the light source is hitting them. This is why for a give sapphire with half/half you can take move it so that light hits in a way that shows no half/half and why still photos are not necessarily accurate representations.


None of what you've pointed to is what people are referring to as "half/half". If you look at Chrono's post two posts above, you'll see the pink spinel is showing half/half. What you've pointed to in my photos is nothing more than extinction AND in some cases (although actually not in the photos I've posted) may be caused by a bow tie effect. A bow tie is very very different from half/half. You can only assess gems head on - not from one side.

I agree with Chrono's assessment of half/half also.

Oh boy! Jackpot! This is very educational! I honestly think I'm not the only person out there that has the half/half definition confused.

Although please help clarify. You mention that Chrono's pink spinel shows half/half. Isn't that the same half/half that I see in your sapphire bracelet? One side is darker and the other side is lighter.

I guess since the far right has half/half and not the others than you are basing it on how dark the dark half looks... almost black. And not just a darker half.

Also, I to be specific about the bowtie effect. It should look like a bowtie, right? In other words, a dark line down the center flanked by ligher areas or a light line down the centered flanked by darker areas. In other words, there is a symmetry in the bowtie effect.
 

chrono

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I only see one possibly half/half in LD's sapphire bracelet, namely the one on the very far right.

Top left - could be shadowing. Definitely zero half/half or perhaps some sort of extinction. The light portion is the body colour, the darker part is regular extinction.
2nd stone from the left - the light part is light glare. The dark arrow is pointing to the actual body colour. That is not extinction.
3rd stone from the left - Again, no half/half. The darker portion points to the actual body colour. The light part is brilliance contrast. Note that it is almost white and very bright.
4th stone from the left (aka right most) - this is the only one with possibly half/half. Almost black at the top, body colour at the bottom, and the delineation is very sharp and clear straight down the middle dissecting the stone into two equal halves.
 

lominoblue

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Chrono|1358270968|3356099 said:
I only see one possibly half/half in LD's sapphire bracelet, namely the one on the very far right.

Top left - could be shadowing. Definitely zero half/half or perhaps some sort of extinction. The light portion is the body colour, the darker part is regular extinction.
2nd stone from the left - the light part is light glare. The dark arrow is pointing to the actual body colour. That is not extinction.
3rd stone from the left - Again, no half/half. The darker portion points to the actual body colour. The light part is brilliance contrast. Note that it is almost white and very bright.
4th stone from the left (aka right most) - this is the only one with possibly half/half. Almost black at the top, body colour at the bottom, and the delineation is very sharp and clear straight down the middle dissection the stone into two equal halves.

Thank you for sharing your "eye." Hmmm... I guess the definition of half/half is much more precise than I originally thought. So half/half has to be almost black half and body color on other half.

However, what if we turned stones 1-3 (left to right) so that they were oriented up and down like stone 4 (far right). In principle they should not show the half/half. It should be comparable, right?

LD honey :) :) :) could you orient the stones in the bracelet so that the one with half/half is pointed vertically up/down and a few of the others are also pointing up/down?

So let me rephrase the question. Is there any oval sapphire that would never exhibit any of the 4 possibilities outlined in the stones with arrows under all light conditions? So, not just half/half but more generally a darker half and a lighter half. Probably impossible, unless a round, right?
 

LD

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Here's another photo of exactly the same bracelet taken on the same day - the colours of the gemstones look slightly different because it's actually a bracelet full of colour change sapphires. If half/half stayed with a gemstone all of the time, you'd expect to see the same phenomena in each gemstone and in each photo, right? Well look at this photo and compare. You'll see that the gems look different and the half half as you call it has disappeared in some! You'll now see different things when you look at the gemstones.

In terms of bow ties - think about this logically - why would a bow tie be perfectly symmetrical? Gemstones are not always cut with perfect symmetry. A bow tie can be a thin line, it can be a thick line, it can have wider triangular looks at the sides or narrower. It can make the centre of the gemstone look darker OR lighter. Again it's a function of cut. I'll try and find you some photos of my gemstones with bowties.

In terms of your questions "is there any sapphire that doesn't show ............" yes of course there is! If you look at the purple one I first posted, that has very very little extinction. Is it possible to eliminate ALL extinction from a gemstone? No because the facets will always show shading - that's how light hits the gem and that doesn't matter if it's round, square, pear, or a weird shape!

sapphire_cc_bracelet.jpg
 

LD

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Oh and by the way - the one you think has half/half actually doesn't! It's a bi-colour colour change sapphire that has different colours at either ends (see below) and both ends turn different colours in daylight/incandescent lighting.

sapphire_colour_change_bi_colour_in_bracelet.jpg
 

chrono

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I do not know the type of cut nor the name of the lapidary. I viewed these two about 2 years ago and kept one, sent one home. My intent was to purchase the blue oval and the rectangular was an extra the vendor sent along for my viewing pleasure. We are good friends and he trusts me with his stones. He has since retired from the business. Unfortunately, since I no longer have the rectangular spinel in my possession, I cannot take more pictures of it.

I am concerned that not only is your definition different but you are not reading the pictures accurately. You are sometimes mistaking body colour as the dark part and sometimes mistaking the brilliant part as the body colour. A bow tie isn't necessarily symmetrical nor placed squarely in the center. Not only that, when the lighting condition is just right, the bow-tie lights up and becomes very brilliant.
 

lominoblue

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LD|1358271409|3356111 said:
Here's another photo of exactly the same bracelet taken on the same day - the colours of the gemstones look slightly different because it's actually a bracelet full of colour change sapphires. If half/half stayed with a gemstone all of the time, you'd expect to see the same phenomena in each gemstone and in each photo, right? Well look at this photo and compare. You'll see that the gems look different and the half half as you call it has disappeared in some! You'll now see different things when you look at the gemstones.

In terms of bow ties - think about this logically - why would a bow tie be perfectly symmetrical? Gemstones are not always cut with perfect symmetry. A bow tie can be a thin line, it can be a thick line, it can have wider triangular looks at the sides or narrower. It can make the centre of the gemstone look darker OR lighter. Again it's a function of cut. I'll try and find you some photos of my gemstones with bowties.


Thanks for the pic. But now they just all look kinda dark so hard to tell. More importantly, where is the sapphire that had the reported half/half? Based on your statement "same phenomena in each photo" would imply that the one with half/half should be there. Plus I disagree... I thought half/half could be found sometimes in vertical but not horizontal orientation if say the light source is directed in one plane. So the best picture would be to show the one with half/half in the up/down direction and all the others oriented in the same direction... up/down.
 

FrekeChild

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I'm really confused what you think is half and half lomino? Now granted, I didn't get a lot of sleep last night, so that may be contributing.

Any species of stone can have half and half extinction. Spinel, sapphire, garnet, any quartz, whatever.

They are elongated stones. As we've been saying it's a function of cut. But, I don't know exactly how you are defining half and half, so maybe if we can clarify that better, it would help?

Also, we cannot post videos to PS or links to our own videos at this point. Believe me, I'd love to!
 
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