34. Gemstone Colour: Charge Transfer and Colour Centres

Explore the fascinating science of gemstone colour, focusing on charge transfer mechanisms, the role of ions, and how treatments like heat affect gemstone hues. Perfect for gemmology enthusiasts and professionals alike.

 key topics

Charge transfer in gemstones

Colour centres and defects

Effects of heat treatment on gemstone colour

Titles

The Science Behind Gemstone Colours: Charge Transfer Explained

Unlocking the Secrets of Sapphire and Diamond Colours

 sound bites

"Blue sapphire's colour is a football match of ions."

"Charge transfer mechanisms reveal gemstone secrets."

Chapters

00:00 Introduction to Colour in Gemmology

02:53 Understanding Charge Transfer in Gemstones

05:35 Oxygen to Metal Charge Transfer

08:28 Metal to Metal Charge Transfer: The Sapphire Story

10:58 Organic Molecular Electron Transition

16:22 Colour Centres in Diamonds

22:39 The Science of Synthetic Diamonds

25:27 Understanding Green Diamonds

27:44 The Mystery of Pink Diamonds

30:48 Exploring Colour Centers in Diamonds

35:28 The Future of Gemmology and Podcasting

resources

Gem-A Gemmology Course - https://gem-a.com/education

Instagram - https://instagram.com/facetnationgemmology

Email - mailto:facetnation@facetnation.co.uk

gemmology, gemstone colour, charge transfer, sapphire, diamond, heat treatment, colour centres, spectroscopy, mineralogy

Transcript

SPEAKER_01 0:14

Hello everyone and welcome to another episode of Facet Nation. My name is Lucinda.

SPEAKER_00 0:19

And my name is Simon.

SPEAKER_01 0:21

And today is an exciting day because we might actually conclude colour. Is that right, Simon?

SPEAKER_00 0:26

Well, more or less, yes. I think we're going to conclude the main bits that relate to colored stones. There's probably a bit of diamond coloring that we won't touch on, but we will include that in our diamond extravaganza, which will probably go on forever as well.

SPEAKER_01 0:39

Don't worry, guys, the band gap is still to come. Today is not that day.

SPEAKER_00 0:43

No, there's no room for the band gap.

SPEAKER_01 0:46

It has indeed been a long road, but arguably this is one of the most important topics of gemology from many aspects, value, beauty, rarity, it all comes back to colour.

SPEAKER_00 0:55

Yeah. Um, I suppose understanding colour and the colour functions allows you to explain a lot of the what and why of gemstones. And uh basically if you can understand that, you can give value to them when you're selling them. So justifying a price tag with a story about how this stone came to be makes the job a lot easier, I think. All these amazing things that are happening chemically and like within the ground, in nature, aided by, you know, understanding of science and then a little flourish by the human hand at the end with the polishing and things is um what contributes to making these things valuable effectively.

SPEAKER_01 1:29

Exactly. And one of my favorite things to talk about with people is actually sapphire, and we are going to touch on what makes sapphire blue in this episode. So this is a great one. We're touching on actually a lot, a lot of the fanfaves, I would say, here.

unknown 1:41

Yes.

SPEAKER_00 1:42

Heliodor?

SPEAKER_01 1:43

Who doesn't love Heliod? Oh no, we're not. Are we talking about Heliodor?

SPEAKER_00 1:46

No one likes it but me. Nobody really likes Heliodor, but you know. Yellowstones get a bit of a bad rip, don't they?

SPEAKER_01 1:54

They do even yellow sapphires like a bit pissy, bit they look a bit radiated, but you know, give them give them a chance. Someone on Instagram was saying that barrels have the most boring crystallography, and I was like, damn, harsh.

SPEAKER_00 2:08

That is that is a bit that's a bit rude, really.

SPEAKER_01 2:11

Got those edge pits, man. Come on.

SPEAKER_00 2:13

Yeah, they've got all manner of different edge pits that you don't actually ever find in real crystals, but whatever. Only in perfect ones.

SPEAKER_01 2:18

Anyway.

SPEAKER_00 2:19

We all have a bit of resorption, don't we?

SPEAKER_01 2:21

I do. So most of what we've discussed so far has been the result of electrons taking energy and giving it back, but they've all been staying within their sphere, right? They're staying in their personal orbitals. Sorry, if you're watching on YouTube, guys, I'm deeply allergic to this mascara. So if I'm weeping, it's not because I'm upset about the causes of color. Some electrons, though, are not quite so obedient, right? Various forces can encourage them out of their little box even further. And it's kind of like Simon says here, the Truman's show of gemstones, there's a bigger world out there. You just need to open your eyes.

SPEAKER_00 2:53

Yeah, at the end of the Truman Shows, you know, when he's like about to escape the confines of the Truman Show and like not be constantly observed by the camera. And he stands at those steps. I mean, if you haven't seen the Truman show, I'm about to ruin the end. He stands at the steps that are like built into the bloody like the sky. You can't even see them unless you're looking at them at the right angle. And he stands there and says his little catchphrase, which is Good morning, and in case I don't see you, good afternoon, good evening, and good night. Gives a little wave and fucks off.

SPEAKER_01 3:24

And that's what our electrons are doing today.

SPEAKER_00 3:26

Yeah. That's more or less what they're doing through the invisible door.

SPEAKER_01 3:30

We've got lots of great metaphors in store for you guys. As we say, we have some fam favorite stones. So let's get started.

SPEAKER_00 3:37

Yes, let's. And what we're talking about today is charge transfer. So we're still talking about ions, and to recap, that's an atom or a group of atoms that possess an overall electronic charge, whether it's positive or negative. That's an unequal relationship between the number of electrons and the number of protons. So I mean this very fact should give you a clue that electrons don't always stay put, because how can they if ions exist? Because that means there's an uneven balance. And like normally, it needs to have the same number of protons, electrons, and neutrons. That's kind of what what happens. So it literally means that some of the electrons are no longer within their own spheres, as it were.

SPEAKER_01 4:18

Much like a bad relationship, electrons want stability, and sometimes that stability is not coming from their home life, their home orbital. Very sad.

SPEAKER_00 4:27

It's very sad. Well, it could be quite liberating, actually, you know, like like Jim Carrey and the Dreamman Show.

SPEAKER_01 4:33

Yeah, they're having their Under the Tuscan Sun moment.

SPEAKER_00 4:36

Yes, that.

SPEAKER_01 4:39

And just like the lady in Under the Tuscan Sun, charge transfer requires more energy to depart their outer orbital than in the case of the dispersed metal ions we spoke about before, where they're just kind of moving between themselves. So this is like a big energy, big deal moment. This is the divorce sequence.

SPEAKER_00 4:57

Yeah, exactly. So that they're still absorbing light energy, and um, there's three ways basically in that they do this, and we're gonna provide examples of each of these ways. So the first one we're gonna touch on is oxygen to metal charge transfer, and then we're gonna go metal to metal charge transfer, and then the non-metal charge transfer. So in the process of ionic charge transfer, electrons are temporarily leaving their original ion, jumping to another one, and then back again, perpetually whilst being illuminated, and this affects the valency state of both the ions involved.

SPEAKER_01 5:30

Indeed, it does. So let's get started. Number one on the docket. So, I mean, you look like you have something else to say.

SPEAKER_00 5:35

No, I don't think so.

SPEAKER_01 5:36

Okay, great. We are starting with oxygen to metal charge transfer. We have talked to you guys a lot about oxygen. It's important. It is everywhere in the Earth's crust. It is the most abundant element in the Earth's crust and makes up 46% of it by mass. So the Earth's crust is heavily oxide and silicon, silicate dominant, and oxygen is a major structural component of both. So it is literally locked into the minerals that build the rocks. Therefore, it's generally the closest neighbor to metal ions and plays a super important role in the process of charge transfer. Simon, tell me more.

SPEAKER_00 6:13

Yeah, so oxygen with an atomic number of eight is nice and small too. So it sort of fits in a lot of gaps, nestles in between larger metal atoms in the in the lattice. Absorption courtesy of this type of charge transfer usually occurs in the ultraviolet, which can extend into the blue end of the visible light spectrum. And this generally causes like yellows, browns, and orange body colors in the material. The specific color caused depends on the actual gemstone itself.

SPEAKER_01 6:41

And we have a wonderful example for you, and that is everyone's least favorite barrel, heliodor. Although I guess gauchenite is actually everyone's least favorite barrel. Alright, so in Heliodor, the electrons are transferred from oxygen, which is O2 minus, to the iron ions, which is Fe3 plus. The oxygen is a ligand, meaning an atom, ion, or molecule that is bonded to a metal ion and donates electron density to it. So oxygen, the ligand, donates electrons, which are temporarily excited to the iron ion, not in a way that permanently alters the valency state. But this temporary excited state means that the isolated Fe3 plus ions effectively behave like Fe2 plus ions, which is what causes the strong UV and deep blue absorption, which means strong yellow coloration, where often the blue is heavily absorbed. And the same thing is happening in other ion-colored yellow gemstones like yellow sapphire and my enemy in nemesis, sinholite.

SPEAKER_00 7:46

Sinolite, yeah. Doesn't get a lot of good press, to be honest. It's just sort of yeah, just another yellow yellow gemstone that nobody really cares too much about. Um I'm sure you can find very nice ones, though. And is obviously named after the language of Sri Lanka, Sinoles.

SPEAKER_01 8:03

Yes, which we do support.

SPEAKER_00 8:06

Yes. Always. So the important thing to remember here is that oxygen, which is the ligand, O2 minus, to metal, Fe3 plus charge transfer equals strong blue absorption and yellow coloration. Now, if you wanted to observe this in the laboratory, you would use UV viz spectroscopy. And that's the most effective way of observing this mechanism and shows this strong broad absorption bands in the UV and the blue regions, much stronger, in fact, than in the examples we gave where the electrons just move within their own orbitals.

SPEAKER_01 8:37

Indeed. And guys, we've got some bad news here. If you are taking the Gem A exam at the diploma level, you need to know these ions and these examples very specifically.

SPEAKER_00 8:48

You do indeed. Yeah. You will be asked to recall this. And there are an exam throughout the course on your online things and all sorts. Like this is stuff you need to know.

SPEAKER_01 9:01

Exactly. So write down these ions.

SPEAKER_00 9:04

Yes.

SPEAKER_01 9:04

All right. Next one. I would say this is the biggest celebrity of the charge transfers. Would you say, Simon?

SPEAKER_00 9:10

That's yeah. Okay. Yeah. There's a good uh there's a good way of remembering this that we've that we've come up with, and it relates back to football again, like all things do.

SPEAKER_01 9:19

So I'll intro it and then let Simon take it away because Simon has a whole football metaphor that I don't even want to get into, but it is lovely.

unknown 9:27

Fair enough.

SPEAKER_01 9:28

So, metal to metal charge transfer. This is drumroll please, what makes blue sapphire blue? As we know, blue sapphire is colored by a combo of titanium and iron, and it's the electron transfer between these two metallic ions, right, that we're thinking about specifically here. Intervalence charge transfer, where they share electrons back and forth, and the ionic charge alters during this process. So we could disappear down. Oh, do you want to go? Do you want to? Is this is this where your metaphor starts?

SPEAKER_00 9:57

No, it doesn't. Like we have to so what we're going to say now is sort of a caveat because we've simplified this a little bit. We could indeed now disappear down an enormous rabbit hole explaining ligands and the deeper understanding of orbitals, including their subshells and the order in which electrons are donated and/or choose to occupy the next shell. Because like throughout this process, we've been saying that you know it goes like two you get two in the inner one, and then you get, is it six in the next one or eight? Whatever. The the shells fill up, two, four, eight, whatever. The shells fill up in a certain order. But then within those orders, they also they take it in turns, and there's a very specific order of how they go to the next one. We're not gonna get into that because it's it's too long, too complicated, because it's not actually really relevant to the actual mechanism and not really something you need to know. So rather than a straying down a bloody garden path somewhere, we're gonna keep it fairly straightforward. Yeah. So we're just gonna aim for a broader understanding, allowing us to pinpoint the reasons and the actual trace elements involved. We've simplified it a little bit. So for instance, in this next example, the metal to metal charge transfer, oxygen is still involved, it remains the ligand environment, but its presence doesn't really alter the mechanism, which is key to understanding intervalence charge transfer. So that mechanism being the swapping of electrons between metals. So while oxygen is there, we're not going to sort of mention it as such. We're just gonna imagine that oxygen is the pathway or the bridge between the two metals.

SPEAKER_01 11:35

Yes, which I really like is a metaphor. I think that makes sense.

SPEAKER_00 11:38

Yeah.

SPEAKER_01 11:38

So in a way, if in your metaphor would oxygen be the pitch?

SPEAKER_00 11:42

Oxygen is not necessarily. I don't know how we would get oxygen. We can sort of f pretend that oxygen isn't there. We're just remembering in the back of our minds that oxygen is the bridge, the gap bridging the gap between them. Yeah. So basically just remember that metal ions are surrounded by oxygen ligands bonded to the ion by way of shared electron density or electron donation, if you like. And something else to caveat as well, there are other ligands, but we only really need to concern ourselves with oxygen in most cases. Exceptions being like fluorite, for example, where fluorine is the ligand. But again, we'll be getting carried away and going down the wrong path and not really explaining. Well, we're here to explain. So yeah, blue sapphires.

SPEAKER_01 12:26

Blue sapphires, iron titanium. It's a football match.

SPEAKER_00 12:31

It is, yes. So we've got ions, V2 plus iron ions, and Ti4 plus titanium ions. And then we've got the oxygen bridges. Yeah? So let's put this into a football scenario. Imagine the score is two plus versus four plus in favour of titanium. So these are their this is an arch rival match. This is like a local derby. Now the secret of the rivalry is that iron has never won this match throughout all of history's history. And I'm sorry to spoil the party. Iron is never going. Iron is never going to win this match. This is it's not happening. There's nothing is set up here for them to win. Their players always get injured like cursed. Time to be a fan of iron. Iron, iron, iron, irons. Let's so let's get to it. When a blue sapphire is being radiated by a suitable light source, electrons jump from one ion to another, and whilst doing this, they transfer their negative charge from one ion to another. So the score was iron two, titanium four, and it then becomes iron, Fe three plus, and titanium Ti3 plus. So it's a draw. We're level. The electron leaves the ion ion, increasing its overall positive charge to Fe3 plus, and joins the titanium ion, decreasing its overall positive charge to Ti3 plus. The score's three, we're level. But rather than the ions pushing on for victory, if you're a fan of West Ham, this might be important to you because their nickname is the ions. They give the ball almost immediately, straight back to the opposition, titanium go up the other end, and they score again. The electron returns, we're back to 2-4, FE2 plus, Ti4 plus. This happens back and forth. Iron never gets in the lead.

SPEAKER_01 14:20

Perpetually on the edge of glory, but can't quite close it.

SPEAKER_00 14:23

Yep. This causes broad and strong absorption, specifically in the yellow-red region, thus transmitting blue.

SPEAKER_01 14:30

Beautiful. A gorgeous metaphor. Definitely one that I had wrapped my head around at some point, but lovely to be reintroduced to.

SPEAKER_00 14:39

Yeah, the important things to remember is two two four three three. Exactly.

SPEAKER_01 14:44

Two four three three back and forth for all of eternity. Or as long as that sapphire is being lit by something. Now, guys, sapphire crystals are often colorless, milky, and opaque in their appearance. Okay, these are known as gouda. Is it guaida sapphires?

SPEAKER_00 14:58

Gouda, I think.

SPEAKER_01 14:59

Gouda like the cheese, but spelled differently. And this milkiness is due to significant inclusions of rootile. Rutile's chemical composition is titanium oxide. So where is this going? If you could liberate the titanium from the rootile and allow that titanium to join iron on the pitch, the pitch, of course, being within the corundum lattice, and resume the brittle ri the brittle, the bitter rivalry, what would happen? Well, this is the whole point of heat treatment, right? That is what heat treatment is achieving with sapphire. So you heat the sapphire. We'll get into the deep mechanics of this because there's a lot of numbers to remember, but broadly, if you heat the sapphire, you dissolve the rotile, and as it cools, the titanium will pair with the iron, which in turn alters the valency state of the iron ions and the game is back on. This is when charge transfer begins. So the crystal is no longer milky, you've dissolved all of that rutile, and it also becomes a beautiful strong blue color. So while some people might be a little bit fixated on having an unheated gemstone, indeed it's a very special and rare thing nowadays because something like 98% of corundum is heat treated to improve or alter the color. These poor gouda sapphires would never see the light of day, and they would never take their place under the bright lights of the football stadium.

SPEAKER_00 16:16

Yeah. So heat treatment's not all bad. Yeah.

SPEAKER_01 16:19

And it's very I mean the Romans were heat treating their corundum. Like, come on.

SPEAKER_00 16:22

Yeah, this is this is your ticket to the cup final. This is this is how we do it. Heat them up, get them ready to go, and then game on. I mean, you're still gonna lose.

SPEAKER_01 16:34

Only if you're a phantom iron. What if I'm a titanium girly?

SPEAKER_00 16:37

Rutile's doing okay, because the rootile is the titanium, but the rootile's getting the rootile is actually turning itself into a player, it's getting involved.

SPEAKER_01 16:45

It goes from the bench onto the pitch.

SPEAKER_00 16:47

Yeah, exactly.

SPEAKER_01 16:48

All it needs is a little excitation.

SPEAKER_00 16:50

Yeah, so there you go. A lovely metaphor. By way of football.

SPEAKER_01 16:55

Next up, this is what Gemma calls non-metal charge transfer. Okay, but we're gonna call it drumroll plays, organic molecular electron transition. I don't know that ours is rolls off the tongue quite as well.

SPEAKER_00 17:10

It doesn't, but non-metal charge transfer, strictly speaking, is not actually entirely accurate.

SPEAKER_01 17:16

All right, tell me more, Simon.

SPEAKER_00 17:17

So this involves organic materials. So organic materials, they're generally made up of larger molecules, hydrocarbons in the most part, so that's hydrogen and carbon, the clue's in the name. And they might have shared electronic orbitals. These orbitals are known as molecular orbitals. So visible light or higher energy radiation can excite electrons to become delocalized from their home atoms and are excited from low energy molecular orbitals to higher energy molecular orbitals. These groups of atoms, molecules, act as the home atom for the electrons rather than just being confined to a single ion. All groups understanding.

SPEAKER_01 17:56

So the the electrons live in a mansion in an open relationship and they're all swingers. So all the electrons leave their mansions and go roaming around, is how I would remember.

SPEAKER_00 18:06

There's a lot of sharing. There's a lot of sharing going on.

SPEAKER_01 18:10

Sharing is caring, y'all. Keys in the bowl.

SPEAKER_00 18:12

A lot of sharing. So the electrons are basically delocalized and transitioned from the orbital to the orbital within the molecular structure. So we're thinking that bigger structure here, rather than just um sort of atoms on their own. We're talking on a molecular, molecular level. Electrons in this framework means lower energy is required for excitation and means they travel further because it requires less energy as they transfer, which results in different absorption and different transmitted colours. Electron transitions of this kind generally produce reds, pinks, yellows, and you're going to find this mechanism in things like amber and coral.

SPEAKER_01 18:51

Yep. And organic dyes are often used to color materials such as jadite, which we have discussed before, guys. So in the example of chromium dye in jadite, chromium acts as the central ion, and the ligands are now the molecule which becomes attached to it and shares electron density as before. This is one other instance where the ligand isn't oxygen, it's a molecule.

SPEAKER_00 19:13

Exactly that. Yeah.

SPEAKER_01 19:15

Now you know.

SPEAKER_00 19:16

Now you know.

SPEAKER_01 19:17

What's your favorite of the charge transfers?

SPEAKER_00 19:20

The ones that don't cause yellow, probably.

SPEAKER_01 19:22

Sorry, Heliador. Another takes another L.

SPEAKER_00 19:25

Yeah.

SPEAKER_01 19:28

So there is another mechanism that we're going to talk to you guys about today, and that is called color centers. These are defects in the crystall lattice or anomalies that absorb wavelengths of light, and there are four types to be aware of. So we've got vibronic, vacancy, electron, and the charmingly named hole. That's with an H rather than a W.

SPEAKER_00 19:49

Yes, the whole. Fucking creepy.

SPEAKER_01 19:52

The whole center. First up and very significant is the mighty N center in diamond. Simon, tell me about that.

SPEAKER_00 19:58

Yeah, so nitrogen, which is the N here, ninety eight percent of diamonds have nitrogen as an impurity. Diamond in its pure state is obviously carbon and only carbon in a tetrahedral lattice. So that's a carbon atom bonded to four other carbon atoms at equal length and distance. When nitrogen is present during growth, it can substitute for carbon and aggregates over time. These aggregates of nitrogen cause different degrees of yellow coloration. The most common aggregate is three nitrogen, so that's the N3 atoms surrounding a vacancy, a vacancy being an empty space where an atom should be in the framework. Now this vacancy causes tension, distorts the lattice, and during light excitation the bonds vibrate, which is where vibronic comes in. But these vibrations cause a characteristic absorption peak at 415 nanometers. This is something to remember in the violet, and that's what causes the sort of yellow body colour. The greater the concentration of the N3 vibronic centers, the more saturated the yellow colour.

SPEAKER_01 21:01

Yep. So remember everybody, 415 nanometers. That is the line you are looking for. You have to do some pretty advanced testing to even see this, though, frankly.

SPEAKER_00 21:10

Yeah, you do, because like your spectroscope, we've spoken a great deal about being able to see absorption bands in the blue and the violet, and basically you can't.

unknown 21:18

Yep.

SPEAKER_00 21:19

So yeah.

SPEAKER_01 21:20

Important to note though, it doesn't happen in synthetic diamonds. So synthetic diamonds generally have the nitrogen removed because they want to produce colorless stones. That's the whole point. But even if they didn't, the growth process is too fast for any any nitrogen to aggregate that way. Just they're like, what? What just happened? It's over. The game is done. They're locked out of the lattice. So therefore, the 415 nanometer absorption line is a key indicator test for natural diamonds. And it's actually the first port of call for a lot of synthetic diamond tests. If only we could see it with a spectroscope, I could impress my friends a lot more at dinner parties.

SPEAKER_00 21:54

But or piss your friends off at dinner parties because you like taking the spectroscope out in bars. You could have a look. At their diamonds and be like, dear, I'm sorry, that's synthetic. I can see the 415.

SPEAKER_01 22:05

I did hear, I did hear that diamond fluorescence cannot be replicated in lab diamonds. That is the word on the street in my studio. I don't know if that's have you heard anything.

SPEAKER_00 22:15

That's um well I mean that's all part of the 415, so it fluoresces differently. We could talk in different fluorescence. Yeah. If you've got blue fluorescence basically in a diamond, then you're pretty much um you're pretty much naturally. No doubt they'll work out ways of fucking f doing this.

SPEAKER_01 22:31

Yeah, doing that. Well, because fluorescence was initially seen as a bad thing.

SPEAKER_00 22:35

Yeah.

SPEAKER_01 22:36

Which I don't understand. I think it's fun. Get the party started.

SPEAKER_00 22:39

So do I. The thing is, like these synthetic diamonds are such low cost now. You can buy them for like next to nothing. I think we're probably turning a bit of a corner on that, but that's a conversation for another day.

SPEAKER_01 22:52

Indeed. But a conversation for today is the GR1 vacancy. This is also in diamonds. And this occurs when a high energy radiation, such as gamma X-rays or electron rays, displaces a carbon atom out of the crystal, out of the diamond lattice, causes a lattice vacancy. It basically just like pings it out through the force of its radiation, which is pretty sick, actually. And this vacancy causes absorption at 741 nanometers in the infrared. And it also causes a green body color, so green diamonds. Irradiation of this kind is usually artificial and undetectable as the symptom of treatment, but it's the same as natural irradiation. So rare naturally irradiated diamonds do occur from radioactive decay. Thorium and uranium within surrounding host rock in the Earth's crust and the damage caused results in carbon vacancies and the same absorption.

SPEAKER_00 23:46

Yes. Now, occasionally when you find rough diamond crystals, they can appear green. And you're like, hello, I've just dug this diamond crystal.

SPEAKER_01 23:54

Am I a bajillionaire?

SPEAKER_00 23:56

And it's green. Um and that's because basically there could be irradiating elements present in the surrounding groundwater or host rock as they're sort of growing or just lying around. But the thing with these crystals is that that green colour generally is only skin deep. And uh when you polish when you polish the stone or facet the stone, that green colour tends to uh tends to be gone, and then you've got a colourless or indeed a sort of slightly yellow stone beneath. If you do the diam the De Beers Diamond Pipeline course at um at De Beers, one of the exercises they do when they take you in the uh heavily guarded rough area is that they sort of tip out this whole bundle of diamond crystals and they basically say to you, You everybody pick up a pick up a crystal and whoever gets the most valuable one is uh is the winner. And a lot of people race and pick up the green ones, but because they think, oh well, green diamonds, green diamonds are really, really rare and really valuable. Actually turns out that that green is probably going to be polished off if they were fasted, and uh those people don't generally win the competition. You don't win anything, it's just sort of like bragging rights. But yeah. Did you win Simon? If you do do I didn't, someone got the pink, the slightly bigger pink one than me. I wound up with a pink one, but it wasn't big enough to win.

SPEAKER_01 25:14

You do love a pink.

SPEAKER_00 25:15

So yeah, if you do the Diamond De Beers pipeline, the De Beers Diamond Pipeline course.

SPEAKER_01 25:20

Don't fall for the joke.

SPEAKER_00 25:22

That's a little trick for you. Don't pick up the green ones because the green ones are not green throughout.

SPEAKER_01 25:27

But there is one green diamond that is green throughout, that is the famous Dresden green diamond. We know that it's definitely natural and that the color penetrates throughout. Well, we believe so. It is a rounded pear shape and it's a type 2A, which means there's no nitrogen as an impurity, and it predates artificial irradiation techniques, so we can guarantee that this color is natural. We know this because records date back as far as 1722. Let me Google her.

SPEAKER_00 25:56

You would hope it was in Germany, but I actually don't know.

SPEAKER_01 26:00

I doubt it.

SPEAKER_00 26:01

A bit of live googling.

SPEAKER_01 26:04

Yeah, it's in the Met.

SPEAKER_00 26:05

Oh, is it? Is it? Yeah, everyone.

SPEAKER_01 26:07

All the good shit's in the Met.

SPEAKER_00 26:08

Oh, not in the Met. Sorry. Not the I've not seen the gemstones in the Met.

SPEAKER_01 26:13

It's really beautiful.

SPEAKER_00 26:14

It's a it's a not the nicest shape, to be fair.

SPEAKER_01 26:17

It's a beautiful colour though. It's kind of a minty green, kind of a you're gonna hate it's like a tourmaline green.

SPEAKER_00 26:24

Yeah, it's a nice colour, but it like the shape's a bit rounded at the top. It's not very pointy. There you go.

SPEAKER_01 26:29

Well, we can't win them all. Next one, my personal favorite, just because it's so fucked up. It's called plastic deformation. Like you go to LA and you pick the worst surgeon, and this causes rare and very valuable pink diamonds.

SPEAKER_00 26:42

Are there bad surgeons in LA? Yeah, I suppose they must be.

SPEAKER_01 26:45

Yes, yes. People are dying getting BBLs in people's garages.

SPEAKER_00 26:49

Would you not be are you better off going to Turkey then where it's cheaper?

SPEAKER_01 26:52

You can go to Turkey, you can go to South or Central America.

SPEAKER_00 26:56

Okay. That's like the Turkey of the Yeah.

SPEAKER_01 26:59

There's a whole, I think if you go, I think it's the DR, the Dominican Republic, you can get a whole package that's like you get your Lipo and your mommy makeover, and then you get a beach holiday to rehabilitate.

SPEAKER_00 27:11

Okay. Yeah, probably don't ask me how I know this.

SPEAKER_01 27:14

The Turkish experience.

SPEAKER_00 27:16

Yeah.

unknown 27:18

No, no.

SPEAKER_01 27:19

I'm you know, I'm open. I'm getting older every day, and I am not a averse to a tummy tuck.

SPEAKER_00 27:25

Okay. Well, well, let us know how that goes when you when you venture off to the Dominican the Democratic Republic of the Congo.

SPEAKER_01 27:32

That's a different DR, babe.

SPEAKER_00 27:34

Sorry, what's Dominican Republic?

SPEAKER_01 27:36

Dominican Republic.

SPEAKER_00 27:38

Imagine going to the Congo. Imagine going to the Congo for a tummy tug. Yeah. Sorry about that. Dominican Republic, of course.

SPEAKER_01 27:44

All right, back to pink diamonds. Plastic deformation. So pink, brown, and purple diamonds get their color this way. And essentially what is happening is a structural defect in the diamond lattice is causing a color center, unlike the GR1 center, which you term a point defect. So this is the whole lattice being a bit like. And that is because a distortion caused by slippage of the bonds along the glide plane. So this defect can extend throughout whilst maintaining mirror symmetry. And it's often associated with color zoning and deformation lamelee.

SPEAKER_00 28:20

Yes, so layers of deformation. And that the pink gets in the gets in the layers along these defects, along these glide planes. There's quite a good diagram of the slippage in the Gemma course notes, which we might or might not remember to share.

SPEAKER_01 28:36

Yeah, maybe. We're gonna try. We're gonna try for you guys. Let me I'll write that down. How about that while you you tell them about the uh electronic structure?

SPEAKER_00 28:44

So the distorted lattice alters the electronic structure and produces a broad, broad absorption band centered at 550 nanometers, giving rise to pink, brown, and occasionally purple coloration. Pink diamonds are or were mined from the now closed Argyle mine in Australia. So the Argyll mine is unique in that the diamonds are hosted in lampro white rather than Kimberlite pipes. But again, we won't get into that now, because we'll speak about that more when we do our diamond series. It essentially means more variability, a bit more stress, and that's what causes the distortions in the lattice and the plastically deformed diamonds, meaning pinks and browns. What people don't really understand is that a lot of the stones that came out of Vargyal are brown, and whilst the pink ones come from there, there's a whole shitload of brown ones that came out too.

SPEAKER_01 29:36

Because it's well it's like everything, there's more shit ones, you know?

SPEAKER_00 29:39

There's mostly more shit ones, yes. But that's why they're it.

SPEAKER_01 29:42

I've I don't think I've ever seen a pink diamond in the flesh, you know.

SPEAKER_00 29:46

Really?

SPEAKER_01 29:46

Yeah.

SPEAKER_00 29:47

Like property. I do know they're so expensive, like tens of thousands of pounds a carrot, even if they're like ten or fifteen pound.

SPEAKER_01 29:56

I just remembered a piece of green diamond lore, which is that Jennifer Lopez's second engagement ring to Ben Affleck is a green diamond.

SPEAKER_00 30:04

Oh, is that right?

SPEAKER_01 30:05

Yes. And she's kept all of her engagement rings, so Bowman.

SPEAKER_00 30:08

Bet she fucking has. Yeah. I would have done too.

SPEAKER_01 30:11

You get to keep them at the second the wedding happens, they're yours, etiquette-wise.

SPEAKER_00 30:15

I think as soon as you've been given it, it's yours, to be honest. You can't be a takerbacker, can you?

SPEAKER_01 30:19

No.

SPEAKER_00 30:20

Unless someone throws it at you in hate and spin.

SPEAKER_01 30:23

In rage.

SPEAKER_00 30:24

Then you're like, okay, well fine, I will have it back in that case.

SPEAKER_01 30:26

So many people in Hatton trying to sell their engagement rings and being like, what do you mean? It's not worth anything. Lots of women I've actually heard saying, like, so how much do you think he paid for it?

SPEAKER_00 30:37

And everyone's like, I'm not getting involved. I'm literally not getting involved in that. No way.

SPEAKER_01 30:42

I think guy dudes just be lying. They're out here lying.

SPEAKER_00 30:45

That's a that's a thing, unfortunately, yeah.

SPEAKER_01 30:48

Anyway, onto our favorite kind of colour center, shall we? Which one is it, siren? The whole colour center.

SPEAKER_00 30:54

The hole. Now do remember this is a hole with an H, because you could get super confused if you were trying to put a W in front of that. Um it's a hole, you know, like a hole.

SPEAKER_01 31:05

Yeah, like something missing. There's a hole there.

SPEAKER_00 31:08

Yes. So it is more common for irradiation to displace an electron rather than an entire atom. And when it does, it leaves a hole in the energy orbital, a missing electron causing absorption. So in the case of smoky quartz, aluminium AL3 plus substitutes for silicon, SI4 plus. Irradiation removes an electron from a neighbouring oxygen, forming a hole center. These hole centers produce broad absorption across much of the visible spectrum, resulting in brown to almost black stones. You can actually reverse this, I think, by heating them, and then all of the electrons sort of go back home and then you can lighten the colour. But if you do that too much too much, then you can actually wind up with it being completely colourless. So you've either got something brown or colourless. Happy days.

SPEAKER_01 31:53

Well the cool thing, smoky quartz is cool because all of this irradiation is happening, we discovered at the GMA conference. From cosmic rays. Like space is irradiating all of this quartz and turning it brown and black.

SPEAKER_00 32:04

Yeah, he was talking about cosmic rays in Switzerland, wasn't he? Which I don't know where they're coming from.

SPEAKER_01 32:10

Cool. Space, dude. They're coming from space.

SPEAKER_00 32:12

Pretty wild. Like like from um Marvin the Martian's gun.

SPEAKER_01 32:16

Honestly.

SPEAKER_00 32:17

That's probably what's happening.

SPEAKER_01 32:18

I'm getting super into space right now and it's actually freaking me out. Did you know we're not only we are like hurtling through space, not just around the sun. Like the whole it's all hurtling. We're all hurtling towards some mass. Well, yeah, there's something, there's a name for it. But it's like this big sucking there's something that's attracting us at the end of the universe, and we're just going towards it. Like, I don't want to go towards it. I want to stay here.

SPEAKER_00 32:45

Maybe you do. Who knows?

SPEAKER_01 32:47

What is it? Anyway, that's a story for another day, inspired by cosmic rays.

SPEAKER_00 32:51

A story we probably won't touch on, to be honest. Not in this podcast. Who knows? We'll start another one.

SPEAKER_01 32:57

Great attractor, that's what it's called.

SPEAKER_00 32:59

Yeah. Hurtling.

SPEAKER_01 33:00

Speaking of great attractors, tron color centers.

SPEAKER_00 33:03

Yeah.

SPEAKER_01 33:04

Great segue. This is also a radiation-related, like all of our favorite color centers. And it's when an atom has been displaced and the vacancy is occupied by a trapped electron. It's commonly known as an F-center. It's actually quite tragique if you think about it, because this electron was just going on its merry way and wandered into the wrong place and now it's trapped.

SPEAKER_00 33:24

And now it's got to behave like something it's really not.

SPEAKER_01 33:27

Yeah, and it's and it's trapped doing this forever.

SPEAKER_00 33:29

It's like, right, step up, big boy. This is your this is your chance. You've got you're not an electron anymore. You're like a fucking you're like an atom. You have to be you have to masquerade now as a as a chemical element. Like, good luck. See ya.

SPEAKER_01 33:44

It's like being in corporate. So this occurs in fluorite, and this trapped electron causes absorption across much of the visible spectrum except the violet, and this produces a purplish color. So uranium in hydrothermal veins create these vacancies during growth and result in the characteristic bandang slash zoning that you often see in fluorite. It can be reversed by heat treatment that releases the trapped electron from the cavity and returns it to its original site in the crystal structure. Truly a liberation story for our times. But this process lightens the color. So it eliminates that color center, lightens the color. But if you heat it too much, you can actually remove the colour completely, which is not what we wanted.

SPEAKER_00 34:26

So I was I basically explained that about the smoky quartz. I might have gotten confused there. It might be that it's the electron colour center that if you heat, you can lose all the colour. So don't quote me on that.

SPEAKER_01 34:38

We'll just we'll excise that part from the or do you want to keep it and we'll just take our chances?

SPEAKER_00 34:43

Maybe we could do a bit of um bit of studying to see if I was see if I was correct. But just text me and let me know. Then maybe just get rid of it. I knew one of them that you if you heated it, you could lose the colour. And it's obviously this one, not the other one. But well. You know, we don't claim to be perfect. I don't mind you keeping this in. I'm not cla I'm not sitting at claiming to be perfect.

SPEAKER_01 35:04

I think it adds a bit of human humanity to the proceedings.

SPEAKER_00 35:07

Exactly, but we don't want people remembering the wrong thing either. So, you know. As long as we as long as we explain that we've got something wrong, then or if someone wants to point out that we've got something wrong, I'm totally happy with that too. I'll just do that.

SPEAKER_01 35:17

Yeah, we'll read your letter on the yeah, we love it.

SPEAKER_00 35:19

Yeah, I'll take it on the chin. Oh shit, I've totally said the wrong thing there. Yeah.

SPEAKER_01 35:23

Correct us.

SPEAKER_00 35:24

We're doing our best, please, God.

SPEAKER_01 35:26

Well, on that note.

SPEAKER_00 35:28

Yeah. So that is that is more or less colour centres, whether it be right or wrong, charge transfer, colour centres, all of that stuff. Take it as it is.

SPEAKER_01 35:38

We were obviously going to talk about band gaps, we're leaving that for another time. I'm gonna put on my course as me.

SPEAKER_00 35:44

Enjoy yourselves, everyone. We'll be back with something, who knows?

SPEAKER_01 35:49

Do we have a little announcement for people, Simon?

SPEAKER_00 35:52

Yeah, maybe we do. As it comes to the summer and people are taking their exams in June, we're going on holidays, the sun shines. We're probably gonna take a little bit of time off. I don't know how long, maybe like a few weeks, couple a couple of months, who knows?

SPEAKER_01 36:07

Nothing tra nothing tragic. We'll still be here.

SPEAKER_00 36:10

We're not going away for good, but as it rolls up to June, we might take a bit of time off, prepare some more notes ready for coming back for the for the new school year. And uh yeah, don't think we're uh we're leaving you. This isn't uh goodbye, we're ending the podcast. We're just gonna take a bit of time off over the summer to recharge. Recharge. Get a time. Yeah, exactly. We'll be back in later on after our little break looking glorious.

SPEAKER_01 36:37

Yes, much fresher. Dinner, tummy tucked, perhaps.

SPEAKER_00 36:40

Maybe.

SPEAKER_01 36:41

But guys, anything's possible. We will still be here, so we'll still be on socials, we will still be dropping occasional, probably much more casual, just shitty chats as things happen in the gym world, a little catch-ups. So if you have any questions, please get in touch with us and we may read them on the podcast. We might do a little mailbag episode, things like that. So as always, you can find us on Instagram at Facet Nation Gemology. You can email us fascination at fascination.co.uk. We do have a TikTok that I'm gonna figure out to log into eventually. Yeah.

SPEAKER_00 37:15

Excellent.

SPEAKER_01 37:16

We love you guys. We hope that you love the color centers.

SPEAKER_00 37:20

Yes, and please, if you um feel like reaching out, then do so because that's the best part of this. So yeah, drop us a message if you feel inclined. We appreciate it.

SPEAKER_01 37:30

Yes. Have a lovely short week, guys. This will be going out on the bank holiday Monday. So if you haven't, Simon's about to go out Morris dancing, it's the chimney sweep festival.

SPEAKER_00 37:39

Yeah, literally, that's what I'm doing this afternoon.

SPEAKER_01 37:42

So I'm gonna go find a May pole tomorrow in a park, unless the we go down Wickerman style. We will see you next week.

SPEAKER_00 37:49

Yes, we will. Thanks very much.

SPEAKER_01 37:51

Bye guys.

SPEAKER_00 37:52

Adios.