Why diamonds sparkle ?

[25362]

Can anyone explain why are there diamonds that lack brilliance and others that glitter strikingly ?

 

[TheBlacksmith]

As I understand it, diamonds sparkle due to light being reflected internally from the many facets. If the diamond has poor light transmission characteristics or the internal interface has poor reflectivity, the diamond will not sparkle as well as a clear, highly reflective one.

Blacksmith

 

[EngineerDave]

Reading that post made me remember the concept of internal reflectance, although I don't think I could summarize it without looking up some info on it.

Diffraction of light plays the key role in that however.

Are you looking to buy a wedding ring soon? LOL. Couldn't resist asking that!

 

[NickE]

I think that the external facets have to be in some relative orientation to the crystal planes in the matl.

then its a matter of the high index of refraction of diamond 2.42 i think.


nick

 

[25362]

All of your answers are right and I thank you for the trouble you took in posting them. It appears that the high refractive index of the diamond, and with the help of proper cutting, all the light can be reflected. Brilliance is also affected by light been broken into a spectrum of colours because of refraction, making multicoloured reflections. Because of diamonds' extreme hardness, the facets never wear off, and -happily- so does their sparkle.
EngineerDave, no I'm not planning to buy a wedding ring, but thanks for the idea anyway.

 

[25362]

By the way, it's interesting to note that when the jobs of cutting and polishing of the facets are finished, the diamonds are plunged into boiling sulphuric acid to clean off all traces of grease and dirt, leaving the diamonds totally undamaged in the process.

 

[NickE]

Yes but diamond is a meta-stable state of carbon and can
x-form into raw carbon.

(IIRC)

nick

 

[CoryPad]

NickE,

Graphite does have lower free energy than diamond, so diamond can convert to graphite if there is sufficient activation energy. By the way, this energy is large.

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[hacksaw]

Boiling sulfuric! I hope they have a good fan.

Believe a heated diamond was used to dispense with the flogiston theory (an the diamond), by placing it into a container of pure oxygen...

 

[hacksaw]

regardless of the purpose of the test with a heated diamond, it would have been quite a sparkler, regardless of the index of refraction or how it was cut...

 

[ornerynorsk]

You all know the 4 c's right? Well, 3 of those c's have to do with the "fire". Color, cut, and clarity. The cut is the single most important factor in turning gem-quality rough into a stone of value and quality. This is why the best diamonds , ie the ones with most "fire' come from the Israeli cutting houses. The precision that goes into faceting a stone would make the precision machining industry quite jealous. You can also do a precision facet on a poor quality diamond or a bort, and you won't get any fire at all.