What causes prism colors?

[Iwanttosparkle]

Hello everyone, this is my first ever post. I've been lurking and reading for a while, but finally decided to register so I could ask questions. My husband and I have been together now 20 years and to celebrate I am about to buy (hopefully) my first ever ACA because what is most important to me is sparkle. What makes a diamond throw different prisms of color (red, blues, greens) as opposed to some that are more just like a shiny silver mirror? Is it a certain angle number of a certain cut like the pavilion angle or the crown angle? I would like to know so that I know what to look for on the diamond specs sheet. Any help is appreciated. Thank you!

 

[lovedogs]

The easiest way to explain this is looking at angles. I'm certainly not on par with many of the experts here, but 60/60 stones (e.g stones with 60 depth and 60 table), will throw more white light. Stones that are considered ideal on these boards (and sold by whiteflahs in their ACA line, or high performance diamonds and their CBI stones) have smaller tables (54-57), and depth between 60-62.4. luckily for you, you've already decided to go with one of the "super ideal" brands (ACA). All of them are cut to these proportions and will throw tons of colored fire. Picking an ACA, CBI, or Brian Gavin signature stone is literally pressing an easy button. You could close your eyes and pick one at random (as long as it's in budget, color preference, etc), and it'll be amazing. You don't need to worry about the minute angle details on those stones, which is great.

So pick any ACA that works with your budget and color/clarity preferences and I'm pretty sure you'll be thrilled.

 

[kmoro]

I agree, you can’t go wrong with any ACA. If you want to study up on diamond performance, your ACA will meet all the requirements for a beautiful, sparkly and full of the rainbow light that you are asking about. If you don’t, you won’t need to worry about it and have a great performing diamond.

To answer your question in the simplest terms:
Diamond fire is the result of dispersion of light. As white light strikes a transparent item (such as a diamond, glass, or water droplets) and passes through, the light rays slow down. In simple terms, this causes the white light to be split into various colors (light refraction). Diamonds have a high refractive index, the higher the index, the more colour light dispersion, which is why diamonds are famous for this effect. This is also the same effect as a rainbow after a rain. However, the diamond light dispersion also depends on cut.



The theory is that, the larger the table (like a 60/60) stone, the smaller are the other crown facets (less room because of bigger table). These facets are the ones that split the light into rainbow colours (they are prisms), so to maximize fire, sometimes at the expense of brilliance, some diamonds have small tables, like 53-55, but ACA range can go a bit bigger with confirmed ideal light performance. Most people looooove fire ... sometimes at the expense of brilliance, but I think there should be a good balance of the two. The Tolkowsky Ideal Cut (TIC) offers a good balance of brilliance and fire, and the ACA is cut for the sweet spot right smack in the middle of the best part of TIC cut parameters. Having said that, there are many 60/60 stones and other cut parameter variations that still produce a good amount of fire and brilliance ... this is because there are a whole bunch of facets and angles in the diamond cut, acting like prisms and mirrors, and ultimately, the performance of the diamond will depend on how all of these work together.

And of course from Whiteflash:
https://www.whiteflash.com/about-diamonds/diamond-education/diamond-fire-1568.htm

I hope that’s helpful and that the experts will come along and correct my errors! lol

Congrats!

 

[Iwanttosparkle]

Thank you to both of you, that was helpful. I read the article and watched the video and I do see a difference in regards to the fire. It's fascinating! I will start taking note of the table sizes from now on of non-ACA diamonds.

 

[gm89uk]

If you really want large bold fire flashes more so than white scintillation, consider an OEC or an AVR style diamond.

 

[cflutist]

Here is a post by John Pollard that explains what our OP is looking for.

https://www.pricescope.com/community/threads/cbi-fire.242606/#post-4388614

 

[Iwanttosparkle]

Thank you everyone!