Ruby clarity question

[Tropicmaster]

I mostly understand the "is it red sapphire or is it ruby" debate. What I do not understand is why most sapphires of any color other than red are very clear, and most of the red variations are very cloudy and included. It being the same stone (corundrum) I would think a red stone would have the same characteristics as a blue stone. I have only seen one really clear red sapphire or ruby IRL, although I am sure there are plenty out there. However I have seen hundreds of clear sapphires in other colors. Is it something to do with whatever trace element( iron?) causes the red color?

 

[ma re]

A very interesting question, to which I have no answer unfortunately - but I'd be interested to find out too

 

[Barrett]

I am by no means an expert on corundum..let me see if this might fly...well the coloring agent in ruby is chromium..it''s also the coloring agent in emeralds...for some reason chromium doesn''t like to let crystals grow..it actually inhibits nice good crystal lattice growth..i don''t know why but the chromium atoms clog up or, like i said, inhibit the crystal from growing...i think this has something to do with why rubies and emeralds are rarely found "clean"..it''s against the nature of chromium to make clean crystals...that is from what i understand but someone more experienced like richard M, richard W., or zeolite can elaborate..or anyone else who knows for that matter

 

[Sagebrush]

Not sure I understand the question. If it's red it's ruby and the debate centers around pink versus red. What is called red sapphire is usually brown-orange-red. Never liked the term. Clarity is clarity, the most desirable is eye-clean, despite publications like The Guide, no one that I know of would pay any sort of premium for loupe clean corundum of any color. The standard is the same be it ruby or sapphire.

Rubies tend to be cloudy not due to chromium but rather the usual culprit is rutile inclusions that tend to be burned out in the heating process. Thus, a natural ruby may have more of a tendency to be cloudy.

I little more explanation please!

 

[Tropicmaster]

Date: 8/23/2009 11:25:16 AM
Author: Richard W. Wise
Not sure I understand the question. If it''s red it''s ruby and the debate centers around pink versus red. What is called red sapphire is usually brown-orange-red. Never liked the term. Clarity is clarity, the most desirable is eye-clean, despite publications like The Guide, no one that I know of would pay any sort of premium for loupe clean corundum of any color. The standard is the same be it ruby or sapphire.

Rubies tend to be cloudy not due to chromium but rather the usual culprit is rutile inclusions that tend to be burned out in the heating process. Thus, a natural ruby may have more of a tendency to be cloudy.

I little more explanation please!

My question is not about red versus pink versus ruby. I am curious why most corundum of the red varieties ( whatever you personally call them) is cloudy and included, while most of the other colors ( again whatever you may choose to call them) are a lot more clear and less included. As I understand things corundum is pretty universally heated so I am thinking it does not have anything to do with heat. To simplify my question- why is there a lot less eye clean red corundum than the other colors of corundum?

 

[Richard Sherwood]

Geeez, that's a great question.

I don't know why, but I do know that it's true that blue sapphire typically crystallizes more clean than ruby. That's part of the reason why if you had a ruby and sapphire of comparable size and equal clarity, the ruby will cost considerably more. It's more rare to find in that clear state.

This factor increases exponentially as you go up in carat size. It's not that hard to find a gem quality blue sapphire over 4 carats in size, while a gem quality ruby over 4 carats in size is a real find, and very costly.

Reminds me of aquamarine and emerald. Same mineral, with different coloring agents. Aqua crystallizes typically clean (and can be found in larger crystals), while emerald crystallizes typically included (and smaller).

Amethystguy might be on to something with his "clogged up" theory.

 

[Barrett]

I learned from dealing with Jamie Hill(who found those giant emeralds in hiddenite.) who told me about the chromium prohibiting the growth of crystals..now that may be just size wise or emerald/ruby crystals forming in general and may have nothing to do with clean vs. not clean..just a thought

 

[Richard Sherwood]

Date: 8/23/2009 11:25:16 AM
Author: Richard W. Wise
Clarity is clarity, the most desirable is eye-clean, despite publications like The Guide, no one that I know of would pay any sort of premium for loupe clean corundum of any color. The standard is the same be it ruby or sapphire.

So you're saying that as long as a ruby is eye-clean, there is no premium for higher clarity?

Let's say you have two 2 carat rubies for example, both indentical to the eye, except one is eyeclean but with many inclusions easy to spot under a 10x loupe, while the other has a single inclusion very difficult to spot.

You don't think the clean 2 carat would bring more on the maket than the more included one?

 

[Colored Gemstone Nut]

Date: 8/23/2009 11:35:28 AM
Author: Tropicmaster

Date: 8/23/2009 11:25:16 AM
Author: Richard W. Wise
Not sure I understand the question. If it's red it's ruby and the debate centers around pink versus red. What is called red sapphire is usually brown-orange-red. Never liked the term. Clarity is clarity, the most desirable is eye-clean, despite publications like The Guide, no one that I know of would pay any sort of premium for loupe clean corundum of any color. The standard is the same be it ruby or sapphire.

Rubies tend to be cloudy not due to chromium but rather the usual culprit is rutile inclusions that tend to be burned out in the heating process. Thus, a natural ruby may have more of a tendency to be cloudy.

I little more explanation please!

My question is not about red versus pink versus ruby. I am curious why most corundum of the red varieties ( whatever you personally call them) is cloudy and included, while most of the other colors ( again whatever you may choose to call them) are a lot more clear and less included. As I understand things corundum is pretty universally heated so I am thinking it does not have anything to do with heat. To simplify my question- why is there a lot less eye clean red corundum than the other colors of corundum?

Hi Tropic Master,

Interesting question, but i think the real issue is your making a generalized statement based on what you have seen.

Quality ruby or sapphire is rare.

With this said, I would say there is a lot of "commercial quality" ruby and sapphire on the market.

To directly anwer your question, I would say there is less eye clean ruby on the market vs. other colors based on what I've seen.

There are top quality goods be it sapphire or ruby and than there is the rest.

 

[PrecisionGem]

I think Josh is spot on here. There is a lot less quality ruby than sapphire, so you see many more included or even opaque stones. There are eye clean stones, but they are expensive.

 

[Barrett]

I have to agree with gene and josh on the amouint of clean vs. not clean. Also if large amounts of silica or iron are present then rubies tend to shy away..now iron can be found in rubies but it will push out the rare chromium atom..since iron is a dime a dozen you have many other colors of sapphire which are colored buy iron by less ruby because less chromium..lots of other colors because lots of iron. The fluorescence of a ruby is tied to its composition, to the low iron. So rubies need aluminum, oxygen and chromium to make one..with chromium being pretty rare in nature and iron being plentiful you will have lots more "other" colors and less rubies. Like josh said quality ruby or sapphire is rare but quality ruby is more rare than quality dsapphire due to chromium being rare as opposed to iron..as for your clarity question..because quality ruby is more rare than quality "other" colored corundum then you will see more that has inclsuions or not as clean looking

 

[chrono]

A very good thought provoking question. I too thought the answer lies in the chromium content and almost all stones with chromium tend to be rather small. However, mine’s only a guess.

 

[marcy]

Very good question and I would completely agree with what Gene said. I think bad rubies are one of the poorest looking gemstones on the market, quality rubies are gorgeous.

 

[PrecisionGem]

I saw a very large and clean ruby while in Tanzania. The stone had to be around 15 or more cts. in the rough. My fear was it wasn''t real. There are lab created stones floating around over there dressed up to look like natural rough. The guy wanted $30,000 for the stone, which was too much too take a chance on it not being real.

 

[Sagebrush]

Richard,

Generally, in the market, there is no premium for cleanliness above eye clean in ruby. I once knew a small dealer who tried to grade by loupe and who would not buy a stone less than a diamond grade of vs, but he was the only one that I know of who would pay a premium. All generalizations are false, there are sure to be a few people, again I am speaking generally.

As for rarity, chromium is rare so ruby is rare and therefore clean ruby is very rare particularly unheated. As I said earlier, heating, actually cooling, tends to clarify the crystal of ruby and for the most part it is rutile that is heated above its crystallization rate and exsolving into the crystal.

 

[Barrett]

Hey richard when you say exsolving what do you mean? That is something i sort of wondered about...what happens to the rutile..do it''s molecules actually break down and enter the alum. oxide crystal lattice?..how does it disappear? never put much thought or research into it

 

[Richard Sherwood]

Date: 8/24/2009 3:40:41 PM
Author: Richard W. Wise
Richard,

Generally, in the market, there is no premium for cleanliness above eye clean in ruby. I once knew a small dealer who tried to grade by loupe and who would not buy a stone less than a diamond grade of vs, but he was the only one that I know of who would pay a premium. All generalizations are false, there are sure to be a few people, again I am speaking generally.

I would tend to agree with you on the bulk of rubies, but would disagree with you on larger, fine to gem quality stones.

I don't know many buyers who given the choice on two stones identical to the eye wouldn't choose a "loupe cleanish' ruby over an eye clean ruby.

Consequently the loupe clean stone would usually command a premium in most markets....dealer, auction or private. Not a premium comparable to a grade (or even half a grade) better hue, but still a premium nonetheless.