URAL MINERALOGICAL FESTIVAL, July 3 to 21, 2019, in Yekaterinburg City, Ural region, Russia
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PostPosted: Mon Sep 18, 2006 12:24 pm 
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Am I the only one wondering if this would be a good thing for DVD's and CD's? Surely I'm not the only one with a little Miss Destructo at home! :smt028

I quite like the idea of being able to coat softer gems so that they can be more easily worn. Maybe it's time to stock up on those beautiful but hopelessly soft gems if this is going to be something that becomes more common.


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PostPosted: Mon Sep 18, 2006 3:18 pm 
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Doos,

Nice pic as usual.

can you clear up a few questions? I'm not sure how far the light would refract towards the normal when passing from the diamond into the CZ. Would this angle be different than the angle seen when light passes from air to CZ due to the different values of optical density between air and diamond as optical mediums.

Also the dispersion on CZ is very high so the seperation of colours which cause it's great "Fire" might affect any calculations. Would this be overcome by measuring/drawing only the nD refractive values?. (In your own example the light ray is at 90 degrees to the table so neither refraction or dispersion would take place until the light hits the pavillion facets.)

Frank


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PostPosted: Mon Sep 18, 2006 4:34 pm 
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Quote:
can you clear up a few questions? I'm not sure how far the light would refract towards the normal when passing from the diamond into the CZ. Would this angle be different than the angle seen when light passes from air to CZ due to the different values of optical density between air and diamond as optical mediums.


The calculation is:
n of rarer material x sin incidence ray = n of denser material x sin refracted ray.
Hence in the case of CZ and Diamond and an angle of incidence of 40°, that wil be:
2.176 x sin(40°) = 2.417 x sin(x)

So, sin(x) = (2.176 x sin(40°)) / 2.417 .. which gives an inverted sine(x) of 35.35°.
For air/Diamond you substitute 2.176 with 1 (the RI of air approx.) and the angle of refraction will be about 15°.

Quote:
Also the dispersion on CZ is very high so the seperation of colours which cause it's great "Fire" might affect any calculations. Would this be overcome by measuring/drawing only the nD refractive values?. (In your own example the light ray is at 90 degrees to the table so neither refraction or dispersion would take place until the light hits the pavillion facets.)


My calculations are done on nD. Dispersion is not taken into account.
You could calculate the dispersion effect if you like .. nB of Diamond is 2.407 and nG of Diamond is 2.451.
For CZ they are: nB = 2.167 and nG - 2.207 I believe (but you may want to recalculate that). But I'm sure it will not make much difference.

My diagram was to show dot/tilt tests effects, not to prove that sugar coating on a CZ would turn a CZ into a diamond. There are many other factors that need to be taken into account. For instance when the light ray refracts into the coating it is not totally refracted. Some parts are reflected inside the CZ.
To the best of my knowledge there is no such thing as total internal/external refraction.

Can you recall yourself wondering why anyone would ever need math in real world while you were in highschool?


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PostPosted: Mon Sep 18, 2006 7:59 pm 
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:smt017


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PostPosted: Mon Sep 18, 2006 8:47 pm 
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Don't feel confused MoDo.
Science can get confusing, but gemology doesn't have to be.
We don't even know anything about this coating and the original post of the company (Serenity) using this technology doesn't offer any information about their technology.

It could be an amorphous carbon diamond like coating or a polycrystalline diamond coating (some sort of CVD) or who knows what else.

This may be more of a chemistry problem than a math problem. Is it coating or bonding with dissimilar crystalline minerals? Does the coating have the same RI as single crystalline diamond?

Does it react the same to a thermal heat probe?
What about UV.

We need to investigate more before making any determinations.
Figuring out critical angles wont identify these imposter's although it's not a bad idea to keep up on your math.

Sounds like a good group project to acquire some samples and use some practical skills to identify these treatments using equipment most of rely on, on a daily basis.

One thing I know for sure is, an emerald wont have a diamonds luster or any other colored gem for that matter. Seems observation will be good start, with coated CZs being a little more tricky, but SG, fluorescence and some other tests may sort some things out.

If it's diamond or CZ, what about inclusions, girdle appearance, bearding, facet sharpness etc.

Don't forget your basic training. :wink:


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PostPosted: Tue Sep 19, 2006 12:55 am 
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Good point, JB!

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PostPosted: Tue Sep 19, 2006 1:33 am 
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JB wrote:
Don't forget your basic training. :wink:


I'm guessing you're not talking about Marine Corps boot camp here :lol: .

Math isn't that difficult for me ... but I never did learn sin and cosin, etc. I kind of remember tangent from my drafting classes, but otherwise I'm :smt101 .


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