<DragonStek> hi brian <BrianQ> hi Bart, Dragon, Phyllis <Phyllis> Hi Brain <BrianQ> that's me... the "brain" ;) <DragonStek> lol <Phyllis> hehee..

Transcription

1 <DragonStek> hi brian <BrianQ> hi Bart, Dragon, Phyllis <Phyllis> Hi Brain <BrianQ> that's me... the "brain" ;) <DragonStek> lol <Phyllis> hehee.. Brian = Brain <DragonStek> either works lol <BrianQ> speaking of color, let's do some warmups! <BrianQ> What color is 532nm? <DragonStek> green <BrianQ> actually, I meant 523nm, but it is the same color. <BrianQ> yes, smiley for dragon <BrianQ> :) <BrianQ> What color is 488nm? <Phyllis> yellow? <DragonStek> blue <BrianQ> actually, I meant 470, but it is the same color ;) <DragonStek> lol <BrianQ> another smiley for dragon <BrianQ> :) <DragonStek> oh i like them <BrianQ> what color is 590nm? <Bart`Flu`zZz> yes, handy knowledge at exam time <DragonStek> orange /yellow cutoff <Bart`Flu`zZz> i'd say orange too <BrianQ> it is the middle of yellow. <Bart`Flu`zZz> ow rats <DragonStek> oh middle of yellow <BrianQ> one can take the blue-green border as 500nm * FranQ has joined #gemology <BrianQ> and the yellow-orange border as 600nm <FranQ> Hi all <BrianQ> hi FranQ <Bart`Flu`zZz> evening ser " <DragonStek> hi <Phyllis> Hello Frank <BrianQ> When you look through the spectroscope, blue-green border marks one third of the scale. <BrianQ> And yellow-orange border marks the two-thirds of the scale. <BrianQ> Frank, we were doing some warmups, guessing color from wavelength. <Bart`Flu`zZz> with orange being above 600, iirc, right? <BrianQ> yes, yes indeed <BrianQ> What color is 690nm? <Bart`Flu`zZz> it's more obvious now i drew the little spectrum rectangle - memories coming back to me ^^ <DragonStek> red <BrianQ> yes, another smiley :) <Bart`Flu`zZz> close to the the ruby emission line i'd say ^^ <BrianQ> indeed <BrianQ> how about 623nm? <Phyllis> orange!! <DragonStek> orange <Bart`Flu`zZz> orange is pretty narrow <BrianQ> yes, phyllis in first this time :) <BrianQ> yes, actually... if you see 623 by itself, you might think it is red...

2 <BrianQ> but if you shine 670nm next to it, then it looks orange... <DragonStek> yeah it gets hard to distinguish where each begins and ends <BrianQ> i.e., it isn't the sort of orange that prisoners on the highway work crews wear. <Phyllis> Yes, I agree with dragon <Bart`Flu`zZz> i miss brown in the spectrum, dunno if it can really be considered as a dark orange <Bart`Flu`zZz> as well as purple/violet or whatever it should be called, halfway between blue and red <Bart`Flu`zZz> 'mauve', yes that was the word ^^ <BrianQ> yes, of course, brown and purple and mauve (magenta) are not spectral colors... violet is, though <DragonStek> but arent you looking at color as a circle not linear <BrianQ> the things you look with... your eyes, have only three separate color detectors. <BrianQ> so if you shine 590 nm light, two out of three (the red and green) are stimulated and you see yellow <BrianQ> and if you shine 532nm (green) and 670nm (red) at the same time, once again both are stimulated, and you see... <BrianQ> what? <DragonStek> yellow <BrianQ> yes. * Pedroq has joined #gemology <BrianQ> So yellow may be the spectral color 590nm or it may be a mix of green and red light. <Pedroq> hello <BrianQ> Magenta, on the other hand doesn't correspond to a spectral color, but it can be created from a mix of red and indigo <DragonStek> so basically we see three colors and depending up which frequencies creat diiferent colors <FranQ> indigo is between blue and violet <BrianQ> ok, so this chelsea filter business! <BrianQ> seems like people attribute magical powers to these filters! <Pedroq> lol <BrianQ> yet they are such a simple thing. <BrianQ> Barbra lists GIA info about suitable uses for chelsea filter... <BrianQ> what is the abbreviation Frank? <Phyllis> CCF <BrianQ> ok, we'll use ccf <BrianQ> especially if you have to look at a lot of pieces of rough, it can help identify odd pieces <BrianQ> What was the original purpose of the ccf, why was it originally developed? <DragonStek> emeralds <FranQ> The Gem-A has a table listing 19 red, green or blue stones and the expected reaction <Phyllis> to easy to seperate a large lot of stones? <FranQ> to differentiate chrome from vanadium as a chromophore in green beryls <DragonStek> to seperate from synthetic emeralds <BrianQ> maybe ok, maybe ok... <FranQ> since Gem_a only allows the chrome ones to be called emeralds <BrianQ> I see... <Pedroq> what the diference between chromophore chrome or vanadium on emeralds? <BrianQ> vanadium absorbs more red than does chrome, apparently ;) <FranQ> the GIA certified a vanadium coloured stone as emerald in the 60's

3 <Phyllis> one quick stupid question first, is chrome different to chromium? <BrianQ> no, chromium ion is the cause of color in ruby, and the chrome on your car's bumper is a chromium alloy <BrianQ> chrome is just shorthand <BrianQ> ok, let's take a look at the whiteboard: <BrianQ> <BrianQ> I sketched a chromium emerald spectrum upon it. <BrianQ> Let me know when each of you can see it. <Phyllis> i can <BrianQ> phyllis has cable internet ;) <Phyllis> Yes.. I live in internet world, need faster connection..hehe <FranQ> Ok I got it...worked pretty quickly tonight <BrianQ> wow! I'm impressed... must be a cloudless sky, Frank! <BrianQ> First thing we can notice is the big bump that peaks at around 525nm. <BrianQ> what color is 525nm? <Phyllis> green <DragonStek> green <BrianQ> yay, those warmups were worthwhile! :) <BrianQ> When we see light, our eyes certainly don't select a single wavelength... <BrianQ> and say that is the color I see... <DragonStek> so blue and yellow wavelenths to make green <BrianQ> What our eyes do is more akin to looking at the total area under the spectral curve and figure out which color is shown most. <BrianQ> Even though the red around 690nm is higher than the green at 525nm, our eyes still say green. <BrianQ> Because we can compare the areas of green and red... as I'll mark on the picture... <BrianQ> Can we see how the green area is bigger than the red area? <FranQ> yes <Phyllis> yes.. that's why...:) <BrianQ> Not to mention that our eyes are a bit more tuned to green than red... so we see a green emerald <Pedroq> hmm weird you should see more red <Pedroq> than you actualy see <BrianQ> Your eyes are not as sensitive to red, and since green is bigger, the overall impression is green. <Pedroq> yes i understoodd :) <BrianQ> Now the ccf only lets through a couple thin slices of the visible spectrum... <BrianQ> Let's take a look at Jean Marie's website to see what you'd see through a spectroscope... <BrianQ> <FranQ> ;0 I love that site <BrianQ> scroll down the page until you find "Filtre Chelsea" and click on that link. <Phyllis> yes, got it <FranQ> Fast phyllis <Phyllis> control F, then type filtre <BrianQ> everyone else? got the little popup box? <Pedroq> didnt find :( <FranQ>

4 <BrianQ> Let's see the ranges that the ccf lets through, according to Jean Marie... <BrianQ> about nm and about nm <BrianQ> agree? <DragonStek> red and yellow <BrianQ> yellowy-green perhaps <BrianQ> Now lets go back and paint those areas in on our emerald spectrum... <BrianQ> I've already painted in the red part approximately... <BrianQ> And now I just added the yellowy-green section given by the ccf... using the color yellow. <BrianQ> Can y'all see both? <Phyllis> yes <FranQ> yes but the green is a bit wide isn't it <BrianQ> If you compare the areas of the two regions to each other, you see the red region has a larger area <BrianQ> compared to the yellow... (yes, probably Frank) <BrianQ> so the yellow area should be even smaller... <FranQ> ah ok just the yellow pen <FranQ> ok <BrianQ> so... if we see (much) larger red area than yellow area, what color are we going to perceive? <Phyllis> red <Pedroq> redish+yellow <DragonStek> orange/yellow <BrianQ> no... we'd see red <BrianQ> as Phyllis says <DragonStek> yup filter we see red duh <Pedroq> so we only see the bigger spectra? <BrianQ> red area is much larger, so the overall impression would be red. <Pedroq> but it s just in this case or extend to all the others? <BrianQ> Let's see... I am going to draw some typical spectrum of green glass... imaginary, but it should serve the purpose... <BrianQ> Now I'll color in the sections that the ccf lets through <BrianQ> remember that the yellowy-green region of the ccf allows both green and yellow, so I tried to show the spectroscopic region of those colors. <BrianQ> What color would the glass appear through the ccf? <Phyllis> yellow <BrianQ> probably green <DragonStek> grreen <BrianQ> or greenish yellow. <Pedroq> green <BrianQ> but definitely not red <BrianQ> so... ccf could be used to separate chromium emerald from this green glass <FranQ> yes <Pedroq> so you go to a database of spectra and compare what is what? <BrianQ> I guess you could. <FranQ> or just learn what stones this is useful for <Pedroq> lol <BrianQ> yes <BrianQ> Originally ccf was to separate between vanadium and chromium emerald... <BrianQ> so what do you think is different between those two mineral's spectra? <DragonStek> one shows more red then the other

5 <DragonStek> or more green /yellow the other way <Phyllis> chromium emerald show red <Phyllis> vanadium show green?? <BrianQ> Yes, I would think so <BrianQ> in other words... the curve would not reach up so high in the red for the vanadium <BrianQ> the vanadium emerald probably absorbs more in the nm range. <BrianQ> ok... so that is about it... that is what the ccf does... compares a thin yellowy-green slice of the spectrum to a thin deep-red slice of the spectrum. <Pedroq> seams that emeralds are relative easy to see <BrianQ> One of the confusions people see with the ccf is they expect a red reaction indicates the presence of chromium. <DragonStek> that was me lol <Phyllis> me too <BrianQ> There is nothing about the ccf that says... "here is chromium!" Instead it says... <BrianQ> "here is more red light than yellow-green light!" <BrianQ> any questions? <FranQ> no <Pedroq> how can you see in this kind spectras the graphics you designed? <Pedroq> the sizes of each spectra <FranQ> Pedro the graphics show what would be seen using a spectrophotometer rather than a spectroscope <Pedroq> ok <Pedroq> is even better then <Pedroq> cause give values and you can get more conclusions <BrianQ> Let's check out some examples of chromium tourmaline, where you can get most any reaction from the ccf <BrianQ> check out this website: <BrianQ> <BrianQ> go to the second graph at the bottom of the page, where it lists red, transition, and green groups. <BrianQ> Let me know when you see it. <DragonStek> got it <Phyllis> yep <BrianQ> Ok, now what that graph is showing is for each group... red, transition, and green... <BrianQ> it shows the location of two deep absorption bands, I and II. The arrows on the right are not meant to represent absorption. <BrianQ> Recall, absorption means the elimination or absence of color. <BrianQ> For the red group, there is an absorption or absence in the range around 400nm and another absorption in the range around 550nm. <BrianQ> What would be the ccf reaction of one of these stones? <DragonStek> green <Pedroq> green <Phyllis> green. <BrianQ> It would be red... the absorption at 550 is absorption or absence of green light (and yellow light) <DragonStek> oops, <BrianQ> no green light at no green light gets through the ccf. <DragonStek> so if it blocks the 550 range only the 400 gets through <DragonStek> hence red coloring from filter <BrianQ> No, the chart is saying that the range is strong absorption and is strong absorption

6 <DragonStek> so those two peaks are why its red <BrianQ> Then there is not strong absorption from nm for example, so that red light would be seen through the ccf. <BrianQ> No, I'm afraid not, maybe you are misunderstanding, because those bars I and II are representing valleys, not peaks. <DragonStek> could be im getting confused <DragonStek> im not sure how to read that graph <BrianQ> They are the dark places in the spectroscope. <BrianQ> the bars I and II. <DragonStek> oh ok i was doing it backwards then <BrianQ> yes <DragonStek> ok got it, sorry <BrianQ> So from Barbra's listing of the GIA info about ccf... <BrianQ> although the Chelsea color filter may be a useful supplemental test, the results give only an indication, not proof of a stone's identity <BrianQ> As I mentioned, this sort of test might be useful when you have to view hundreds of stones, and maybe someone has thrown in some bits of green glass. <Phyllis> yes, it's a supplement <BrianQ> So it is not something to depend upon. <Phyllis> that's what Antoinette said too, and anything show wierd reaction, then it's a warning sign thats what i understood it as <BrianQ> Other tools serve the same sort of purpose. Looking at lots and lots of aquamarine through dichroscope, you can investigate the odd ones (have to plug the new tool I just played with this week) <DragonStek> i like the dichroscope too, but not al stones show a good definition of different colors <BrianQ> Exactly... <BrianQ> But you can identify suspicious examples., <BrianQ> But the real chore... I guess this is the final exam in GIA and FGA, is identifying a stone from scratch... <BrianQ> and ccf is not a tool for that job. <DragonStek> so newbies would be better off with a dichroscope then ccf i agree <FranQ> me too <DragonStek> but its all the tests that lead to the id of a stone <Phyllis> for exams purposes, CCF is not that useful. <BrianQ> yes and yes <DragonStek> i wonder why its on my testing sheets then? <DragonStek> seems a waste of time <BrianQ> the ccf is a supplementary test, I guess to help confirm other tests. <DragonStek> but it looks good to have all the boxes filled in right <DragonStek> so the last test really <BrianQ> perhaps. <Phyllis> but i guess if you are in a show, it's easier to spot the strange stones??? <FranQ> it's also handy for seperating quickly natural blue coloured stones from artificial or synthetic blue stones <BrianQ> Yes, I think so Phyllis... in those aspects yes i agree <FranQ> since many of these use cobalt as a colouring agent and this also shows up bright red <BrianQ> Like I say... it is useful to alert you to oddballs. <FranQ> yes

7 <DragonStek> but on exam paperwork, last to add confirmation to id, yes agree <Phyllis> yes.. <Phyllis> i don't use it at all for my ID.. <DragonStek> oh its on mine paper <BrianQ> Well everyone, I must sign off... talk amongst yourselves ;) <DragonStek> but i fill it all in just to show but mine is different then <DragonStek> thanks brian <Phyllis> thank you very much brian!! <FranQ> Thanks Brian <Phyllis> and have a nice day! <BrianQ> ciao ciao <FranQ> :) * BrianQ has quit IRC ("Java user signed off" ) <Pedroq> cya <Phyllis> has anyone think of why can't we rank the lustre in 1 to 10?? why do we have to use vitreous? adadmantine, dull, pearly, waxy etc etc?? <DragonStek> they like decriptive words <Phyllis> it's difficult for student.. <FranQ> Phyllis if you say 1-10 then how do we know if it's waxy or pearly or earthy or any of the other non normal shiny ones <DragonStek> i know <Phyllis> but jade can do A, B, C.. surely u can do something for lustre <FranQ> do your ID then assign the lustre thats in the book <Phyllis> is just a conversation with my friend, and it makes me think..hahaa <FranQ> exams aren't a good time for arguing with the coursework <DragonStek> it is hard but most are viterous, <Pedroq> is alwys bad time to arguing with teachers <DragonStek> lol <Phyllis> i put most thing as viterous.. <DragonStek> me too <DragonStek> i figure its just a point <DragonStek> if all the rest is right <DragonStek> ok guys, its late by frank so ill say good night <FranQ> I'm going to bed guys <FranQ> cya all next week <Phyllis> good night Frank!! <Pedroq> cya frank :) <Phyllis> See you all next week i got to go too <DragonStek> noght frank hugs <FranQ> hugs :) <DragonStek> sweet dreams * FranQ has quit IRC ("Java user signed off" ) <DragonStek> night <Phyllis> pedro I got to go too.. <Pedroq> ok <DragonStek> see ya next week <Phyllis> see you next week.. <Phyllis> bye bye