Red Garnets and Extinction

[jstarfireb]

Hey guys...while I'm awaiting the arrival of my pinkish red rhodolite from Barry, I've been hearing a lot that red garnets in general are prone to extinction. Redfaerythinker's liquid flower garnet from Uli is a good example.

On the other hand, I have a small malaya from Barry that has a mostly red color with a little bit of orange and very little extinction. It's probably a pyrope/spess mix. It doesn't photograph well, and even this photo shows more extinction than it has in real life.

So is it only almandine/rhodolite that tend to go dark, or all reddish garnets? Show me your brilliant, non-extinct red garnets!

 

[T L]

Jstar,
Not all red garnets go extinct, but many do, including pyrope, almandine, spessartite and their mix. To find a more pastel shade or a stone that doesn't go extinct, is difficult to do. Whenever shopping for a red or orange family garnet, you should always ask the vendor about tone and extinction.

 

[Richard M.]

I think you may be confusing terms here. Extinction is usually caused by cutting a stone's pavilion too deep. Light inside the stone can't reflect back to the eye evenly, resulting in dark areas when the stone is viewed face-up.

The red/purple garnets are sometimes too dark in tone to produce bright gems no matter how well they're cut. Tone is the lightness or darkness of a gem material -- imagine a scale with white as zero and black as 10. No amount of cutting skill can turn a too-dark garnet (or other gem material) into a stone with great optical performance. They remain black holes, absorbing nearly all the light that enters unless the culet facets are cut below the critical angle to "window" them and let more color through. But that's usually an unsatisfactory compromise.

Fortunately there are lovely red/purple garnets of light to medium-dark tone that yield very attractive gems.

Richard M.

 

[jstarfireb]

Thanks, TL and Richard! So why is it that red garnets in particular tend to be overly dark in tone? Is the same true for other colors of garnet?

 

[T L]

Thanks, TL and Richard! So why is it that red garnets in particular tend to be overly dark in tone? Is the same true for other colors of garnet?

It's just the nature of the material. Some gems are prone to being dark, like chrome diopside, chrome tourmaline, blue spinel, although some can be found lighter in tone.

Any kind of garnet, with the exception of some of the yellow grossulars, can be prone to being too dark. That inludes spessartite, green grossular (tsavorite), pyrope, almandine, etc. . .

However, there are lovely examples of brighter gems in those varieties as well. They're just not as common and usually more expensive per carat, especially if the saturation is very good.

 

[zeolite]

rhodolite heart , 2.25 cts

 

[zeolite]

chrome pyrope, 1.06 cts

 

[Richard M.]

So why is it that red garnets in particular tend to be overly dark in tone? Is the same true for other colors of garnet?

It's not just true of red garnets. Many gems -- spinel, sapphire, tourmaline and others -- can be overly dark in tone. As I type I'm looking at a deep blue spinel that would be quite valuable if the tone was lighter. The reason tone differences has to do with the degree that light spectra are absorbed as they travel inside the gem. Light absorption is related to the gem mineral's chemistry and optical factors -- you can spend a pleasant hour or two Googling for more information on the subject.

Richard M. (Rick Martin)

 

[zeolite]

chrome pyrope, 1.08 cts

 

[jstarfireb]

Ooh, Zeolite, those are gorgeous!

 

[movie zombie]

pyropes of larger than 1 carat are notorious for over saturation.....and command an excellent price when not. the smaller ones are less prone.

yes, all stones are subject to over saturation...and that's why its necessary to educate oneself.

i'd love to own a spinel.....but unfortunately i've seen really excellent ones w/o the dreaded "black" and while my budget would allow for something less expensive, i can't stand the thought of only have glints of glowing color on my hand peaking out from the dark.

mz

ps wish i'd done my homework and been into color gems 20-30 years ago when spinel was inexpensive. i will probably never own a another pyrope garnet as 1-i like larger stones and 2-i don't want that black look. yes, that implies i've had a pyrope.....and not knowing any better, i was pleased it was a real stone.....now i can't even look at it. sometimes that education has its disadvantages!

 

[empress]

It may have more to do with the color red (its position in the spectrum) than the gem species (and blue, too). Both seem to be adjacent to black - maybe making them more susceptible to blacking out.

If you wear a red wet suit - it appears black underwater.

 

[T L]

Vivid red is the most desired and one of the rarest colors in nature. When a red gem is light in tone, it is pink, when it is very dark in tone, it goes more brown. It is very difficult not only to find red gems of a more medium tone, but ones that are very saturated. For example, top quality Burmese rubies are valued because they have a very pure and spectral red that appears to glow, and they do not have a dark body color, nor do they have any brown, or even orange. I say orange because it often spills into red since they are next to each other on the spectrum. For people that are '"red purists," often the only gem that will do is a fine Burmese ruby. For my part, I have never seen a gem more red that that. Red garnets, or any red gem in my opinion, just cannot compare imho, but at least if you find a garnet of a medium tone, it will sparkle and be more pleasant to look at than a "black hole."

Burmese ruby

 

[jstarfireb]

Interesting, so it sounds like pure red is harder to find than pure blue, green, etc. Good thing I'm not really a fan of pure red! I like that the rhodolite coming to me is pinkish.

 

[arjunajane]

Hi Jstar,

I recently had just the same conversation with Barry as he had some sent me some reddish pink garnets and we were discussing the
nature of them 'blacking out' in some lighting.
For the most part, my understanding is the same as what others here have said:
1. Red in itself is quite a dark colour, that doesn't really have 'shades' (ie. a lighter shade of red is pink).
2. It is about the tone of the material in question.
3. And the same problem applies to other species of darker colours, such as blue spnel, chrome tourmaline etc.

Here is some of what Barry said on the subject for a little more info:
"The main problem, once again, is iron. It's the problem component for spinel, garnet, sapphire
and even ruby. The rhodolites are a transition garnet, part pyrope which has no iron and part almandine which has quite
a lot of iron. Your umbalite acts the way it does because it's a transitional garnet but it's part pyrope and part spessartite.
The iron content is quite low, so it doesn't black out like the rhodolites. Iron content is why you'll only see people selling
genuine rubies in certain kinds of light. In fluorescent light they can look pretty bad. Synthetics look good all the time
because they leave the iron out.
You can actually have some fun with the garnets. You fill a bowl with water and make a little raft out of bubble
wrap. Then you put the garnet on the raft and you'll be able to pull it around with a strong magnet. If you do the same
thing with your umbalite, I doubt if it will win the boat race. "

(to clarify, I was asking in comparison to an Umbalite of mine that doesn't black out in any lighting condition, and was wondering why this wasn't the case with Rhodos).
Here are some photos of that Umbalite:

 

[jstarfireb]

Very interesting, AJ! Hopefully my rhodolite will turn out to be anemic then.

Your umbalite is gorgeous in that James Meyer setting! I don't recall seeing it before (maybe you posted more about it before I started hanging out in CS).

 

[arjunajane]

Very interesting, AJ! Hopefully my rhodolite will turn out to be anemic then.

Your umbalite is gorgeous in that James Meyer setting! I don't recall seeing it before (maybe you posted more about it before I started hanging out in CS).

ha, good one jstar
It's a Gene PG stone, I went looking for the thread for you but can't find it in PS2
I posted in SMTR at the time, and there's a tonne of pics..

I will look again and post if I can get you the link.

 

[T L]

Iron is one of those chromophores that is the kiss of death to color on some, not all, gemstones. It also inhibits fluorescence, and fine Burmese rubies fluoresce, hence their beautiful color is partly due to the fact they contain no iron.

 

[movie zombie]

Very interesting, AJ! Hopefully my rhodolite will turn out to be anemic then. quote]

now that is funny!

mz

 

[AustenNut]

I've just started giving some thought to a red stone, and since rubies and now most spinels are out of my budget, I was thinking about looking for a garnet. Those garnets of Zeolite are AMAZING in their redness...didn't know garnets could come that red. Of course that probably means they're getting ruby or spinel prices.

Any recommendations of vendors who carry good red garnets? I know Barry has some, and didn't know if there were any others who carry this stuff more often.

Also, umbalite garnets are apparently low on the iron scale. Are there any other "anemic" types of garnet?

 

[chrono]

Yes, the larger the specimen, the worse the darkening on certain red garnets. It seems to be inherent to the material and there’s just no way around it in the larger sizes unless one searches very long and hard and is prepared to pay the price.

 

[T L]

Very interesting, AJ! Hopefully my rhodolite will turn out to be anemic then.

now that is funny!

mz

I heard "pigeon blood" contains no iron, hence the comparison to fine rubies.

 

[chrono]

Here is a good explanation about the tone, which explains that as the tone darkens, the stone will look blacker until the point it becomes almost completely black. It does not matter what hue it is, even if it is yellow, as the example shows. Saturation or rather the lack of saturation also plays a role in the apparent blackness. If too desaturated, the stone will appear browner or grayer. So combined together, if a stone is desaturated and too dark in tone, it will appear blackish as shown in the blue sapphire example.
http://www.palagems.com/quality_4cs.htm#color

 

[T L]

Thanks Chrono, it should also be noted that black is not on the visible light portion of the electromagenetic spectrum. Red, Orange, Yellow, Green, Blue, Indigo and Violet are the only hues that exist in that range.

If you are an abstract thinker like me, I think of color in a three dimensional way. If you have an x, y and z axis, think of the hue as X, the tone as Y and the saturation as Z. You can plot any coordinate in this three dimensional space and come up with infinite combinations of hue, saturation and tone. The science of color is extremely fascinating and complex.

 

[movie zombie]

If you are an abstract thinker like me, I think of color in a three dimensional way. If you have an x, y and z axis, think of the hue as X, the tone as Y and the saturation as Z. You can plot any coordinate in this three dimensional space and come up with infinite combinations of hue, saturation and tone. The science of color is extremely fascinating and complex.

i like that. yes, color is fascinating and complex.....and that's w/o factoring in that we individually see color differently, not to mention what our monitors do to it.

mz

 

[zeolite]

jstarfireb: Ooh, Zeolite, those are gorgeous

AustenNut: Those garnets of Zeolite are AMAZING in their redness...didn't know garnets could come that red

Thank you. Yes, they are amazing. But they are examples of color and tone in garnets that are possible, and not what you are likely to find in the gem market.

The rhodolite heart is possible to find, if you search long enough. It is colored by iron, as are 99% of red garnets. The color in that picture is accurate. The real life color of both chrome pyropes is more saturated and intense than my pictures show. This is because the color saturation in my monitor is limited by the phosphors on my CRT screen, and highly saturated gems can exceed the color gamut of any computer monitor.

Red chrome pyropes (mostly from eastern Arizona and adjacent New Mexico), are very consistent in color. They are not usually orangy red or purplish red, but are blood red. Their red color is more saturated than any other garnet, because their intense color is caused by chromium, the same chromophore as in rubies. Chrome pyropes are very small, very dark, and rarely more than ½ carat when cut. The very rare 1 to 2+ carat cut ones are extremely very dark, almost black

The 1.08 ct red chrome pyrope was created, not purchased. I knew what I wanted, and knew that it did not exist in the present gem market. I searched through more than 500 chrome pyrope rough crystals, for the lightest tone crystal I could find. This was not easy, since some crystals appeared to be lighter, when they actually had the same color density, and only appeared lighter because they were thinner or smaller. The crystal I selected actually could have yielded a 1.8+ ct finished gem, even considering excellent, optimum cutting angles. But I knew it would be too dark. I decided that it should finish at slightly over one carat. I sacrificed finished weight, dollar value, and size and concentrated only on ideal tone, to maximize color and brilliance.

The 1.06 purplish red garnet (my avatar) is even more astounding. I was offered one single crystal of Arizona chrome pyrope, of a color I have never seen, before or since (remember my comment about how consistent the color of Arizona chrome pyropes are). I knew at a glance at that crystal, how stunning it would become.

TL: For people that are '"red purists," often the only gem that will do is a fine Burmese ruby. For my part, I have never seen a gem more red that that. Red garnets, or any red gem in my opinion, just cannot compare imho

That is understandable, given the red garnets appearing in the normal gem market. After both chrome pyropes were cut, I took them to the AGTA show in Tucson. This wholesale only gem show features some of the finest cut, but un-mounted rubies, emeralds, and sapphires available anywhere in the world. I didn’t show them to the public, or to jewelers, but to three full time professional gem dealers, whose specialty is rubies. I presented the 1.08 ct gem to them with no comment as to what gem it was. All three took it to be a ruby! I showed the 1.06 ct purplish red chrome pyrope to several professional fancy (all colors but blue) sapphire dealers. All of them thought it was a plum sapphire!

Richard M: No amount of cutting skill can turn a too-dark garnet (or other gem material) into a stone with great optical performance. They remain black holes, absorbing nearly all the light that enters …

I have one cut and several very purple almandite garnet crystals from Orissa (eastern India). The garnets are sometimes marketed as grape garnets. I was trying for an intense but brilliant purplish red garnet. The cut grape garnet I have, finished at about 1.8 cts, but even with perfect cutting angles, it is inky dark. That crystal could have finished with good cutting angles at perhaps 3 cts. I was trying to duplicate my success of the 1.08 ct red pyrope, but even at 1.8 cts, the grape garnet failed the tone test. It isn’t even worth trying on my other grape garnets crystals. They have beautiful colors in transmitted light, but cutting them is hopeless.

I have good contacts with the GIA Research Dept, and they provided me with complete chemical analysis on my CC spinel, CC sapphire, and the 3.17 ct yellow grossular garnet that was written up in Gems & Gemology. I should submit my 1.06 ct purplish red chrome pyrope, which has intensity and brilliance far beyond any grape garnet I have ever seen. My guess is chemical analysis would show chromium and vanadium, with quite low iron content, compared to most normal garnets.

 

[AustenNut]

Is there a shape that does better at avoiding or minimizing the black spots that garnets are known for?

 

[T L]

Mr. Zeolite,
Do you know if your garnets lack iron? Do they fluoresce as well?

 

[zeolite]

Is there a shape that does better at avoiding or minimizing the black spots that garnets are known for?

Round brilliant would give the most light return and lower the extreme darkness. But notice that both of my chromes are (square and rectangular) emerald cut. This cut best shows the exceptional color.

 

[zeolite]

Mr. Zeolite,
Do you know if your garnets lack iron? Do they fluoresce as well?

They do not fluoresce and I know they contain some iron. But I surmise that the iron content is much lower than normal. Otherwise the purple red chrome pyrope could not show its exceptional brilliance.