28. Colour: Pleochroism and Colour Filter Gem testing

In this episode, Lucinda and Simon explore the fascinating world of gemmology instruments, focusing on colour filters like the Chelsea colour filter and pleochroism testing methods. Learn how these tools aid in gemstone identification and enhance gem cutting techniques.

Educational

 key topics

Colour filters in gemmology

Chelsea colour filter purpose and use

Pleochroism and its significance in gemstone identification

Testing for pleochroism with London Dichroscope and calcite dichroscope

Importance of light source and gemstone orientation in testing

Natural vs synthetic gemstone identification techniques

 key frameworks

Colour absorption principles

Pleochroism and optical anisotropy

Gemstone orientation and cutting strategies

Titles

Mastering Gemstone Identification: The Power of Colour Filters and Pleochroism Tests

Unlocking Gem Secrets: Chelsea Filter and Pleochroism in Gemmology

 sound bites

"Record your observation by stating the colour scene."

"Always think about why you're looking at the stone."

"Share your pleochroic observations with others."

Chapters

00:00 Introduction to Colour Filters in Gemmology

01:55 Understanding Pleochroism and Selective Absorption

05:27 Testing for Pleochroism with the London Dichroscope

10:34 Comparing the London Dichroscope and Calcite Dichroscope

15:36 Documenting Pleochroism Observations

17:35 Understanding Gemstone Colours and Pleochroism

20:04 The Chelsea Colour Filter: A Gemstone Testing Tool

26:23 Practical Applications of the Chelsea Colour Filter

28:50 Identifying Gemstones: Colour Responses and Observations

resources

Gem-A - https://www.gem-a.com

Pleochroism in Gemstones (Book) - https://www.amazon.com/pleochroism-gemstones

Instagram - https://www.instagram.com/facetnationgemmology

Email - facetnation@facetnation.co.uk

gemmology, colour filters, Chelsea filter, pleochroism, gemstone identification, gem testing, gem cutting, gemmology tools

Transcript

SPEAKER_01 0:14

Hello, everybody, and welcome back to Facet Nation, a Germology Podcast. I'm Lisenda.

SPEAKER_03 0:19

And I'm Simon.

SPEAKER_01 0:20

And today we are going to be talking about some very clever instruments. They may not seem like much, you may get them confused every once in a while, but each is very special in its own way and has its own thing to tell us. Simon, what are we talking about today?

SPEAKER_03 0:34

We're going to be talking about colour filters, specifically the dichroscope and the Chelsea colour filter.

SPEAKER_01 0:40

Yeah. And these may look they look a little bit innocuous in the Gem Kit, I guess, next to like all the big scary stuff and next to the refractometer, but they're super useful and great pub equipment, pub testing.

SPEAKER_03 0:52

They look quite cheaply put together, don't they?

SPEAKER_01 0:54

They do. I've fully lost my gyroscope. I threw it away.

SPEAKER_03 0:58

I think there's a I think there's a reason they look cheaply put together, and I think it has something to do with them being cheaply put together together. But nonetheless, they work and do uh do a quite a useful job.

SPEAKER_01 1:11

And I also will say they're great for impressing people and testing set jewelry. So I was in the studio the other day and there was a Tanzanite in a pendant. Wap that on the back lamp, do a little dichroscope magic, everybody's impressed. You get to exp explain pleochroism. Lots of applause, I would say.

SPEAKER_03 1:32

Yeah, very good. Obviously, this episode continues on under the bracket of colour. So um there's still plenty more to come from colour. We're not going to leave uh leave it behind just yet. So in the last colour episode, we told you about the spectroscope and selective absorption. And this time, obviously, we just told you, we're moving on to the um to the colour filters.

SPEAKER_01 1:55

We are indeed. And so one thing that you're gonna want to know as we talk about these is cast your mind back to selectic selective absorption. It is back in play here. So if you haven't listened to those first two episodes, maybe go back, give them a listen. It's really handy for context because you need to understand what selective absorption is so that you can understand how these instruments work.

SPEAKER_03 2:17

Yeah. Um so we told you that you need to be conscious of pleochroism when you're using your spectroscope, uh, because pleochroism affects selective absorption. The different wavelengths are absorbed in different directions of view in some uh optically and isotropic materials. Um so let's tell you a bit about um pleochroism. Assume you have a gemstone that is a cube shape, yeah? And now it's not because it's not a cube because it's crystal habit, it's a cube because we've made it into a cube. And on said gemstone cube, we've written numbers, so now it's a die. Like you play Monopoly with. Oh, it's got six sides, it's got the numbers one to six written on it, right? Very simple.

SPEAKER_01 3:05

Very simple. And beautiful, I'm sure.

SPEAKER_03 3:07

Yes, actually, I would quite like one of them. You know, you get those nice die dice in casinos in Vegas.

SPEAKER_01 3:15

I don't know about that, but I do know about like Dungeons and Dragons hardcore collectible dice.

SPEAKER_03 3:20

They've got more than six faces, don't they?

SPEAKER_01 3:23

Some of them. D6, D20, D eight.

SPEAKER_03 3:26

Right. None of them made a gemstone. Take offense at that, I think.

SPEAKER_01 3:32

It's a compliment, actually. But anyway, tell me about your beautiful gemstone die.

SPEAKER_03 3:37

Okay, right. So um back back on back on track. White light, which we've now told you, I think about five thousand times, has all of the colours of the visible light spectrum all vibrating in all the directions. As we also know, light entering in an isotropic material separates that light into two plane polarized rays, vibrating perpendicular to each other. Are you following?

SPEAKER_01 4:00

I'm following.

SPEAKER_03 4:01

Good. In some cases there is a difference in the selective absorption of these two rays. So different wavelengths being absorbed and different wavelengths transmitting to the eye. This is differential selective absorption, and it means that the material will appear different colors depending on the direction of view. Now this is pleochrobism.

SPEAKER_01 4:22

Indeed. So let's take our oh gone.

SPEAKER_03 4:24

No, no, no, you tell us about the dye.

SPEAKER_01 4:26

All right, so we've got our gemstone dye. Let's say it's made of unheated tanzanite, which is a really good choice for reasons that will become clear in just a moment. So if you shine light through the back of your dye and you look through the face with the number one etched on it, it's blue. If you turn the dye a little and you're looking at the face with the number two etched on it and look through, it's violet and purple. Same thing again. You rotate it a little bit, you look through the number three face, and it's going to be yellow and brown. Obviously, as with all things in life, it's not quite as simple as this, but that the process of turning the dye and shining light through it and seeing these different colors helps you understand that. Sorry, my cat is like fall over me. It basically helps you understand that in the same material, you can see a different color purely by looking at it through a different direction. It's pretty rare to see something as beautiful as this in this particular example, um, and to see it with your plain eye, but it does exist and it's an important way of identifying a material. And there's we were actually just learning about, yeah, some very beautiful mermaid tanzanite, which Victoria Reno's like mermaid unicorn peacock tanzanite on her and Justin Prims website, which is MagisGems.com. Go check it out, guys. I was actually showing some clients this the other day. It's so beautiful.

SPEAKER_03 5:44

Yeah, I absolutely love them. And it's really interesting that you can exploit pleochroism for creating those excellent, amazing colours. Absolutely. Victoria's particularly good at doing that.

SPEAKER_01 5:58

There is one direction that you're not going to see this change of colour, though, is there, Simon?

SPEAKER_03 6:02

Yeah, so pleochroism doesn't occur along an optic axis, much like a lot of things don't occur along an optic axis. If you don't know what an optic axis is, then you've not been listening to all our episodes because we've told you this multiple times as well. But it is a direction of single reflection, refraction in a doubly refractive material. Yeah. Pleochroism. We have actually also sh told you that in uniaxial materials there are two principal vibration durations and therefore might differentially absorb and produce two pleochroic colours. Now this pleochroism is known as dichroism, whereas biaxial materials have three principal direction vibration directions and might produce three pleochroic colours, and this is trichroism.

SPEAKER_01 6:47

Very special.

SPEAKER_03 6:48

I specifically said might show three pleochroic colours because biaxial materials can also show no visible pleochroism at all and show dichroism, so just the two colours. And it is also important to mention that you can only see a maximum of two vibration directions in any orientation.

SPEAKER_01 7:07

Exactly. So always be spinning, guys. Some gemstones that might show you unaided pleochroism, some of my favorites of all time. I just think it's amazing. Some tourmaline and deleucite, all the colours of the autumn, and iolite, which when I first saw blew my mind. I had no idea it was going on. So I think that's a good one.

SPEAKER_03 7:23

So that's a tricksy one, isn't it? Because it can look like lots of things, and the pleochroism is actually quite a handy little info.

SPEAKER_01 7:31

So how do we test for it, Simon, since it's so useful?

SPEAKER_03 7:34

Yeah, so testing for pleochroism brings us to the first about colour filters. And it's useful because if you see pleochroism of a gemstone, it can't be optically isotropic. So it's important to test for pleochroism. So this helps to test between uh like your red spinel, which is obviously isotropic and there's no pleochroism, and ruby, which is anisotropic, uniaxial and dichroic, for example. Also, it's useful, like we just said, for when you're cutting stones, because if you are aware of the pleochroic colours in a stone and you're able to orientate your facets in such a way that exploits the colours, just like Justin told us, his favourite stones are um emeralds to cut because you never really know what colour they are because they've got that sort of yellowy green and the bluey green all coming in together. And um he likes to fashion stones so that you kind of can't tell, and you're seeing all the different colours sort of reflecting around and yeah, pretty, pretty neat.

SPEAKER_01 8:33

Yeah, and Simon, you're coming along really well with your gem cutting. And I think you'd agree that this is one of the great jobs and puzzles that you're trying to solve as a lap is you're trying to retain as much weight as possible, but also cut the most beautiful stone. And so choosing the direction where the colour is the most striking in these pleochroak stones is really important.

SPEAKER_03 8:52

Yeah, absolutely. Because like when you're sort of assessing your rough, you're not just assessing for the yield, because trust me, you waste some material. You need to, if you've got like particularly expensive or like like rubies, for example, you're gonna want to orientate it so you've got your best colour first. And tourmalines like it can look really dark if you're in the wrong direction. So yeah, like pleocrosin is actually very important for a lipidary gem cutter.

SPEAKER_01 9:19

And on your gem exam as well. So we test and observe And on your Gem A exam. So the way that we're gonna test and observe this is by using the London Dichroscope. So it's a pretty simple contraption. It's got two polarizing filters on a little bit of plastic. But instead of being in sequence like with a Polaroscope, these filters are side by side. So they're still positioned with their polarizing directions at 90 degrees to each other. It's just that they are right next to each other so that you can see the two directions right next to each other and compare them and in that way observe any changes in the color directly, which makes it hugely helpful. So it's basically a plastic disc with the filters at the center. And these filters are like two little semicircles right side by side, so you can just see what's going on immediately.

SPEAKER_03 10:08

Yeah, it's got that that motion that you just did is very typical of testing something for player crystal and you're sort of like wafting it over the stone.

SPEAKER_01 10:18

Exactly.

SPEAKER_03 10:19

So well, actually, we're now going to tell you basically how you how you go about testing with your London gyroscope. So yeah, you need a light source. You always need a light source because as we've discovered to great effect on our Instagram, and the most the most the post that's had the most views of any is the one where we say if there is no colour or if there is no light, does colour exist? And I just say no.

SPEAKER_01 10:45

Which is tough but true, brutal, but in its honesty.

SPEAKER_03 10:49

That's the best post we have done on Instagram ever, apparently. So yeah, brilliant.

SPEAKER_01 10:54

Yeah. We're explaining to Simon the concept of a hook. Fuck's sake.

SPEAKER_03 10:58

What is this world we live in? Anyway, you need a light source. And in this instance, we are going to use the flat lamp, a diffused light source, and we place the stone onto the flat lamp, then we come in with the diaposcope and we do the we do the wafting motion, we hover it over the gem material being tested, and we uh yeah, move it around, move the gemstone around, move it in all different directions and orientations and stuff. See what's going on.

SPEAKER_01 11:22

Exactly. And obviously you're rotating your stone because you never know where your optic axis is, and what you're looking for is this change in color. It can be subtle, it cannot exist, you can make it up in your head, and it is worth mentioning that your stone doesn't actually have to be faceted or totally transparent. It does need to have color, obviously, because what you're looking for is the change in color. But this is a really useful instrument because we can do it on rough, we can do it on beads, we could do it on cabochons, we could do it on faceted gemstones, set gemstones. As long as some light can get through, you're good to go with your gyroscope. If you have an opaque gem, however, you are SOL.

SPEAKER_03 11:58

SOLICE.

SPEAKER_01 11:59

Shit out of luck.

SPEAKER_03 12:00

Okay.

SPEAKER_01 12:00

Is that very American?

SPEAKER_03 12:03

But like all Arab American listeners are going to appreciate that. So I think you're all good.

SPEAKER_01 12:07

Shout out to the homeboys.

SPEAKER_03 12:08

Shit.

SPEAKER_01 12:09

Also remember luck. Also remember, guys, to be always be rotating. I mean, this is true of almost every test, but they're optic axes, but you're also looking to see if your material is trichroic or dichroic, as Simon mentioned. You can only see two colours at once. So if there is a third one, you need to find it by twisting.

SPEAKER_03 12:29

Definitely find it by twisting. Also, if the material is particularly pale, then it might be difficult to see any pleochroism.

SPEAKER_01 12:35

So Did you ever have those moments when you were testing Simon where you were like, is this changing colours or am I crazy?

SPEAKER_03 12:41

Or am I just sort of casting a bit of shade or am I just viewing it in a different direction and the light?

SPEAKER_01 12:46

Is it the colour of the filter? Like, I don't understand.

SPEAKER_03 12:50

Honestly, so much of this stuff is guesswork. I hate to hate to break it to you, but you're most of the time you're just going that meh, I think so.

SPEAKER_01 12:57

Information gathering and then making a call.

SPEAKER_03 13:02

Yeah, more or less. Yeah, so but so basically what's happening here is your filter is filtering out the one colour, it's showing you the other colour, the other direction, the vibration direction, and you're seeing the two colours, hey presto, that, ladies and gents, is your London dichroscope.

SPEAKER_01 13:17

There's another kind.

SPEAKER_03 13:18

You have to mention the other kind, even though I've never actually used one.

SPEAKER_01 13:22

But there is a I've never even seen one. Have you seen one?

SPEAKER_03 13:26

Nope. Don't think so. Basically, there's another kind. And if you are a GIA student, so a GGU.

SPEAKER_01 13:34

I have seen one. This is what my boss was using. I was like, why is she looking down this tube? And now I understand.

SPEAKER_03 13:39

Okay, fine. So that will be the GG version of the um of the dichroscope, and it is called a calcite dichroscope. And like you just said, it is a tube. It is a tube with a cleaved calcite block, isolate spar inside it. Apparently it has a lens at one end and an aperture at the other end.

SPEAKER_01 13:57

It looks like a spectroscope.

SPEAKER_03 13:59

Yeah, I think I think a lot of the um like GIA things are quite sort of tube. So you've got like quite a few tubes in your kit. Um yeah. We have we have fewer tubes.

SPEAKER_01 14:13

Yeah.

SPEAKER_03 14:14

So yeah, looks like that. Just the one really. Yeah.

SPEAKER_01 14:18

Although I'm not gonna go into everything that looks like a tube. Go on.

SPEAKER_03 14:22

So it has so it has a lens at one end, which I just said, and an aperture at the other end. And and it's it's got calcite in it because calcite, as we as we know, has a very large birefringence, and the two plane polarized rays are separated such that you can see the two divergent rays side by side through the lens. So that's how it works. Basically, it is sort of separating those rays so far apart that you can sort of see them operating differently and separately. Uh from what I can tell, the London dichroscope, in its simplicity, is a a bit easier to use, does exactly the same job, and um probably less jubi and easier to carry around with you.

SPEAKER_01 15:02

Um I'd say it's also more fun because other people can see what you're doing when you're using a London dichroscope. It's not a solitary experience. So you can really show people it's yeah, it's my party trick.

SPEAKER_03 15:14

That's actually quite a nice reason for using the London over the over the calcite one. I think the issue here is actually that GemA sort of um invented the London dichroscope and GIA are very happy about using it because they didn't invent it.

SPEAKER_01 15:31

I think that's really what's going on.

unknown 15:33

But whatever.

SPEAKER_01 15:34

Controversial. You know, we we know where our allegiances lie. So we're not doing this for fun, guys. We are doing this for hashtag results. So you need to state them. And when you do, this is how you should do it. So first you want to say whether the pleochroism is strong, distinct, moderate, weak, or very weak. And then you want to say how many colors you observed. So for example, if you have Tanzanite, you would say strong trichoism, three colors seen. One, blue, two, violet, three, yellowish brown. And that so and you can kind of draw half a conclusion for that or whatever, but this is kind of the minimum of what you need. Yeah. I always forgot to number them. Don't number them.

SPEAKER_03 16:14

Yeah, I think I got told off for not numbering them. So I think it's quite important for you to number them.

SPEAKER_01 16:20

And it really is like a say what you see kind of situation. So what could you see in some various gem materials? We're not going to go over all of them because Simon thinks lists are boring. I actually think lists are God's gift to the planet, but we'll keep it brief.

SPEAKER_03 16:36

I had a book once as a kid, and I think it was like the big book of lists. That sounds amazing.

SPEAKER_01 16:42

Like, what were some of the lists?

SPEAKER_03 16:44

I don't know, like the best selling records of the last hundred years or something. And he had to have a list and then there were lists of all manner of things. I'm sure it was called the Big Book of Lists. I think that maybe as well as the other thing. Some pick a few.

SPEAKER_01 17:02

A handful. Right.

SPEAKER_03 17:04

So the way this is the way this is going to work, I've ordered these into columns. The columns are species, variety, body colour, pleochroism, and it goes a little something like this. Species, beryl, variety, emerald, body colour, green, pleocroism, scene, blue green to yellow green.

SPEAKER_01 17:24

Very nice. I think a beauty. Species, beryl, variety, aquamarine, body colour blue, pleochroism, colorless, sky blue. I feel like I'm doing the shipping forecast.

SPEAKER_03 17:35

Exactly. Like which is not riveting, is it?

SPEAKER_01 17:40

Drift off to sleep as we Alright, what's next on the list?

SPEAKER_03 17:44

Next up, called cats, is a species of curundum variety, ruby, body colour, red, pleachum, red, orangish red. And that's the that's an important one, actually, for like when you're when you're cutting stones, because you don't really want that orangeish red face up in your stone. So you want to be orientating the table facet so that your red is coming straight through. That's a good one.

SPEAKER_01 18:08

Next up, species corundum, variety blue, sapphire, body colour blue, pleochroism blue, greenish blue.

SPEAKER_03 18:16

Nice. Species iolite variety, also iolite, body colour blue, pleochroism, right, there's a lot of these, violet blue, pale blue, pale yellow or colourless. And this third one is the important one, and that's known as the colour drop. So love it. If you if you've sort of wafting your thing around and you're like, whoa, where did the colour go? And actually with eye light, that's kind of eye visible too. If you're shining a light through your eyelite crystal or wherever it is, uh, and moving it around and you're like, whoa, the colour's gone. It's probably highlight.

SPEAKER_01 18:49

Well, and if you've ever seen eye light, you might think it's a pseudate doublet or like something crazy's going on, but it's just what eye light does, Queen.

SPEAKER_03 18:56

Pretty gnarly. The colour drop is actually pretty, pretty cool.

SPEAKER_01 18:59

It is. Topaz, a little less cool. So it generally shows two or three shades of the body colour. So that can be pink, blue, or yellow. Yeah. Less exciting.

SPEAKER_03 19:07

Tourmaline, similar sort of thing. Two shades of the body colour, you white. Generally, one is light and the other one will be dark.

SPEAKER_01 19:14

And then tanzenite, we've discussed at length. You've got your blue, your purple, and your colourless slash yellow, unless it's heat treated. And then just the two, sadly.

SPEAKER_03 19:23

Yeah. So the London Dycoscope or the pleochrosum test is um useful for certain, particularly in certain scenarios like your iolites, your tanzanites, tourmalines, things like that. And useful if you're a lipidary, as we keep mentioning, but it's never diagnostic. So don't just rely on this. Do some other tests as well. Uh bother your ass to do it properly, please.

SPEAKER_01 19:46

Yes. And don't forget, guys, there is another colour filter in your gem kit. She's often overlooked, but she was made in the swinging sixties. It's the Chelsea colour filter. I always like to imagine people in bell bottoms like leaning over a bunch of emeralds creating this.

SPEAKER_03 20:01

In West London.

SPEAKER_01 20:02

Yeah. They were all at the Chelsea College of Art, weren't they?

SPEAKER_03 20:04

Is that right?

SPEAKER_01 20:05

Yeah. So cool.

SPEAKER_03 20:07

You're always good for it. Amazing haircuts. Historical context.

SPEAKER_01 20:11

I like an anecdote, it's true.

SPEAKER_03 20:13

So what is the Chelsea colour filter?

SPEAKER_01 20:16

It's not a polarizing filter, Simon. It's, as the name says, a color filter. It was actually developed by Jim A. Shout out to Jim A. So we've got two icons of the gem testing kit, even just in this episode. And essentially what it does is it transmits only red 9-0 nanometer region and yellow-green five, seven, zero nanometer region of light. It's also not diagnostic, but as with all these other tests, it forms a wider picture and endorses the other tests that you'll do. And it was actually developed for a very specific reason, Simon. Hit me with it.

SPEAKER_03 20:49

Yeah, so it was initially developed to distinguish emerald from its simulants. Now emerald simulants used to be quite simple back in the day, and they were more or less like green glass or things like that. And emerald would transmit red wavelengths, which is unusual for a green stone, and your green glass would not do that. So if you're using your Chelsea colour filter on an emerald, it might look a little bit red. But actually this test is no longer going to be very helpful for you because synthetic emeralds exist and they also transmit red, probably better than natural emeralds, actually. Yeah.

SPEAKER_01 21:28

Bit of a boohoo moment for the for the for the lads, but such is life. It does still have many uses. First and foremost, maybe assessing parcels of gemstones. If you have a shitload of stones that are all one colour and you want a quick way to initially separate them, Chelsea colour filter it meant.

SPEAKER_03 21:44

Yeah, because if they're showing different colours through the Chelsea colour filter, they can't possibly be the same material because they are absorbing different wavelengths of light, and that's not going to be consistent with the same with the same material. If they look different under the C C F they are Different simple as that really.

SPEAKER_01 22:01

So how do we use this guy, Simon?

SPEAKER_03 22:03

So you're going to place your gemstone on a white background and you're going to illuminate it or them with a light source. Now this is where your MAG light or your fibre optic light comes in handy. It is important that it is a MAGLIT, like a halogen bulb or a fibre optic, because as ever, we need all the colours of the visible light spectrum in play. Um yeah. So you're basically shining it at the stone until it glows.

SPEAKER_01 22:30

Glowing.

SPEAKER_03 22:31

Yeah. Making sure it sort of has got plenty of light in it. And then place the filter up to your eye this time. Don't sort of waft it around in front of the stone. Place it up to your eye. Think of Sherlock Holmes with his magnifying glass while he's inspecting things.

SPEAKER_01 22:47

All those things he inspects.

SPEAKER_03 22:49

All those things. He always carries a magnifying glass. He must be inspecting something. And then look at the stones through the filter. Different colours seen suggest different gem material, and they can be separated into groups for your further testing. Very handy.

SPEAKER_01 23:04

Very handy. And how are we recording? Well, I'll tell you, Simon.

SPEAKER_03 23:08

Please do.

SPEAKER_01 23:09

This one's actually super simple. You're just saying what you see. So record your observation by stating the color scene. So, for example, CCF line, bright red. That's always a fun one. And can also indicate what could possibly be causing the color, what elements you might be looking at. For example, if chromium is dominant with its characteristic absorption pattern, the gemstone will transmit red. Always really fun ones. So this is rubies, emeralds, chrome tourmalines, chrome diops, savarite. The presence of iron can affect this, but you know, chromium, she loves to show up and show out. Whereas cobalt-bearing stones will also tend to transmit red or pink. So you think like synthetic blue spinels, blue glass, all those lovely cobalt blues, they'll be red or pink under your CCF.

SPEAKER_03 23:53

Yeah. And probably one of the most helpful um uh uses of the CCF is separating your blue tapez from your aquamarine. So 100%. Let's say you've got a big large bag of stones and they are sort of this pale sky bluish colour. Um, and you're like, they look like aquamarine. Or ooh, they look like blue topaz.

SPEAKER_01 24:18

Actually, well, one of which is very shit, and one of which is actually quite expensive. And the right.

SPEAKER_03 24:23

Not very, not very shit.

SPEAKER_01 24:25

Topaz.

SPEAKER_03 24:26

But yeah, like quite quite shit, I would have said. Not very shit. Some people like blue topaz. Like, let's not offend people.

SPEAKER_01 24:34

All right. Sorry to the sorry I'm a hater. Go on.

SPEAKER_03 24:37

Sorry to say yeah. So what's that one that I always hate? Uh the fucking goldstone. Yeah, fair enough.

SPEAKER_01 24:43

Yeah. Your nemesis.

SPEAKER_03 24:44

Anyway, the the large parcel of the blue.

SPEAKER_01 24:46

To the point, guys, that if I see goldstone, I will send Simon a picture.

SPEAKER_03 24:50

Yeah, that's I don't I don't enjoy that. Okay, so back to the large parcel of the blue stones. Yeah. Look at them through the CCF. The pinkish yellow ones are likely to be topaz, whereas the greenish ones are going to be your aquamarines. So quite distinct colours there. You're not going to be able to get them confused. And um, yeah, actually really helpful for because Topaz and Aquamarine do look very, very similar.

SPEAKER_01 25:13

They do, and this does not require you to unset the stone, which is really nice. So you especially if you're like on a buying trip or looking at some antique piece of jewelry, you can just CCF it and then you know pretty much where you are. With one important caveat, Simon, what is that?

SPEAKER_03 25:28

Yeah, so the CCF cannot distinguish between natural and synthetic stones. And actually, if the response is particularly bright, so for example, if you've got a ruby and you look at it through the CCF and it is like glowing red, if you like, then you want to be slightly, slightly suspicious of that because it means your chromium is pretty uninterrupted, there's no iron in there at all if it's really, really bright. And as we know, that's very rare, or indeed a symptom of it being synthetic.

SPEAKER_01 25:59

Impossible in nature. I mean, whether and we say this for almost every test, right? If it's too good, ask some questions.

SPEAKER_03 26:06

Always, if it's too good, ask some questions because yeah. And also sort of think about the environment you're in, think about why you're looking at the stone, think about who it belongs to, why you've got it. And if it seems unlikely for you to have a 200,000 pound stone in front of you, it probably isn't going to be one.

SPEAKER_01 26:23

Bright side, you can use the the CCF with faceted and unfaceted gemstones. So if you're wondering about your rough, this is one that you can use on the side of the mine.

SPEAKER_03 26:33

Yeah, perfect. So carry your um CCF and your gyroscope with you everywhere you go, particularly the pub and the side of the mine.

SPEAKER_01 26:41

Our two favorite locations.

SPEAKER_03 26:43

Yes, exactly.

SPEAKER_01 26:44

Uh we will now return to our soothing sleep program for a list of some CCF responses to be aware of.

SPEAKER_03 26:52

Yeah, um, so we're gonna begin with green body colour stones. So green body colour stones, like an emerald. So synthetic or natural stones are going to have a red to pinkish or greenish actually, if there is significant iron involved.

SPEAKER_01 27:06

Alexandrite, pink to red.

SPEAKER_03 27:08

Green glass is gonna appear dull green, which is, you know, what we were saying earlier about the emerald. Good for testing emeralds, even though the synthetics ruined it like they do everything.

SPEAKER_01 27:19

Demantorid garnet, pink to red.

SPEAKER_03 27:21

Yep, that'll be the chromium. Jadite, green, maybe some tinges of pink red if dyed, or if um a particularly nice chromium rich imperial type.

SPEAKER_01 27:30

Whereas a pseudo emerald, dull green. And these do look really sad. They look really sad.

SPEAKER_03 27:36

Yeah. Um bluestones. So blue sapphires, synthetic or natural, remember that. Um look dark green.

SPEAKER_01 27:45

Aquamarine, as we said, will look green.

SPEAKER_03 27:48

Blue spinel, but green-ish. Yeah. Blue spinel is gonna be greenish or it's going to be red in the very rare case that it might be coloured by cobalt. So the next one is synthetic blue spinel, which is gonna look red, because that is coloured by cobalt, but you do in very rare cases get a natural cobalt. Blue spinel.

SPEAKER_01 28:11

So either you've got something very expensive or you've got something that is absolutely not again.

SPEAKER_03 28:16

Think about your environment, think about what you've got in front of you.

SPEAKER_01 28:19

If you have a blue topaz, it will appear pinkish.

SPEAKER_03 28:22

Yep. And that blue glass as well, which is also coloured by cobalt, is gonna appear sort of red or pinkish. Most of the cobalt and chromium ones are gonna be light red or pink.

SPEAKER_01 28:33

Redstones. Shall we start with the big boy?

SPEAKER_03 28:35

Let's start with the big boy.

SPEAKER_01 28:37

Ruby, natural or synthetic. Doesn't matter. They will be red to bright red.

SPEAKER_03 28:41

Yeah, and sometimes really bright red.

SPEAKER_01 28:44

Very fun.

SPEAKER_03 28:44

Garnets like the pyropalmandine end of the garnets are gonna look dark red.

SPEAKER_01 28:50

And last but not least, red glass will be dark red.

SPEAKER_03 28:52

Yeah. Um there's lots of types of red glass, and I think most of them are still gonna look dark red. So Yeah.

SPEAKER_01 28:59

If you're trying to tell them apart, spectroscope's your girl.

SPEAKER_03 29:02

Hundred percent, yes, which we've already told you about. So yeah. That's the colour filters. That's plear chroism. Thanks for listening. We've got more colour episodes coming up.

SPEAKER_01 29:12

We're gonna talk about so many directions we could take this sermon.

SPEAKER_03 29:15

We're gonna take it, we're gonna tackle iridescence and that sort of chisel next. And then we're gonna get into charge transfer and all of that.

SPEAKER_01 29:26

I think valency state is what the people are baying for.

SPEAKER_03 29:30

The valency state of ions. That's what gets me out of bed every day.

SPEAKER_01 29:33

Yeah, I definitely fully understand it. No, I do. I do, don't worry.

SPEAKER_03 29:37

Well, we're gonna we're gonna recap it and make sure everyone understands it.

SPEAKER_01 29:40

So, guys, we hope that you enjoyed this episode. Tell us, drop us emails. Have you seen a Pleochrogue stone? What is your favorite Pleochrogue stone? And a loose site for me, I must say.

SPEAKER_03 29:51

Yeah, you like the old um autumn, the autumn or autumnal things, don't you?

SPEAKER_01 29:55

And its pleochrousm is so strong that every time I see it, I scream. I'm like a child.

SPEAKER_03 29:58

I've got another shout-out actually to do before we wrap this up.

SPEAKER_01 30:02

Yes, Simon.

SPEAKER_03 30:03

A guy called Silas messaged us and uh he was very enthusiastic and kept sending us little short videos, which unfortunately I don't think you can go back and watch anymore because they were like, once you've watched it, you can't watch them anymore.

SPEAKER_01 30:14

Oh, like Snapchat.

SPEAKER_03 30:16

Yeah, he's um he was very enthusiastic, very kind. So shout out to Silas for messaging us.

SPEAKER_01 30:21

Thank you, Silas, and thank you for listening.

SPEAKER_03 30:24

Somebody else might have messaged us as well, but I can't remember who, so we'll give them a shout out in the next one. But yeah, we've had a couple of nice messages this week. I hope you've liked the interviews that we've done. We are trying to find some others. Please give us some feedback on this sort of stuff and let us know what you enjoy. Um, obviously, we're going to keep going on about the um mechanics of being a gemologist, but uh any extra curricular stuff that you want us to try and tackle, then please get in touch and let us know.

SPEAKER_01 30:55

Yeah, let us know if there's anyone in the trade that you're really interested to hear from, or if there's, you know, if you want to hear from gem traders, if you want to hear about localities, we're always here. You can reach us on Instagram at Facet NationGemology, or email us facetnation at Facet Nation.

SPEAKER_03 31:12

Perfect. Um, actually, I um connected with someone quite interesting on LinkedIn this week. So watch this space. That could be a very good one.

SPEAKER_01 31:26

Interesting. Well, on that cliffhanger, guys, we will leave you. Thank you so much as always. Catch us on Instagram, guys. I want to hear all your gem gossip. Come and chat to us in the stories.

SPEAKER_02 31:35

Yeah, please do.

SPEAKER_01 31:37

All right. Happy jamming, guys. We'll see you next week.

SPEAKER_02 31:40

Thanks a lot. See you bye.

SPEAKER_01 31:41

Bye.