Advise on Fancy Diamond Shapes (and high fire coloured gems)

[TristanC]

Dear All,
I am actually looking for a round shaped fancy coloured diamond - due to my preference for the shape.

To be honest, my very limited experience so far is entirely with colourless diamonds, so I love the fire and brilliance of the round cuts.

This is where I would like for people with experience with fancy coloured diamonds in particular, and with gems that exhibit more fire and scintillation and sparkly bits to chime in on:

1) Their favorite shapes and why - pertaining to colour
2) The effect that the shapes have on colour and sparkle in their experience

I'm not lucky enough to have a retail store with fancy diamonds nearby to walk into and annoy the sales people... So looking for wisdom here instead

 

[kenny]

Re: Advise on Fancy Diamond Shapes (and high fire coloured g

Don't forget they cut FCDs for color strength not light return.
Even if you find a round in your color there's a good chance it is not going to score under 2.0 on the HCA - not that GIA even reports the four numbers needed to calculate the HCA.
They don't.
If it has a full GIA report for colored diamonds you'll get the depth % and table %.
Often rounds are cut deeper than 62% to give the light more material to travel through to strengthen the color.

Even if it only got the abbreviated GIA Color Origin report it is easy to calculate the depth % . . .
Divide the depth by the diameter. (They are on every report and are expressed in mm.)
Then multiply by 100.
If it is too far over 62% it is not going to have super light performance.
Even if it IS near 60% they still may have put the table too high or low, which you can discern in the side view.

Sometimes the vendor will have a side pic,
After you get used to seeing where the girdle should be placed you will be able to spot when they put it too high or low.
These are tricks to guess the cut quality for light performance but is just a rough ballpark thing.
You really have to see it live.

You might get lucky if you look long enough to find a round that also has kicken light performance.
When you do it's a joy.
My FI Green round OEC has it, and it's worth every penny.
When you move that thing around in spotlighting it's light performance holds its own, even next to our ACA, Solasfera and Octavia.
All the planets were lined up when that guy was cut.

All shapes can be cut poorly or well for light performance.

Since FCDs are so expensive you are likely to get a small carat weight compared to a colorless diamond.
The Emerald cut will have the largest facets of all cuts.
That mean larger flashes of light.
The body color itself is not so much a flashing event; it's just always there.

 

[TristanC]

Re: Advise on Fancy Diamond Shapes (and high fire coloured g

Thanks Kenny, always glad when you chip in.

I realised it was really hard to use the HCA since I couldn't get angles...

I really want a gem that can hold its own in terms of cut - which is why fancy diamonds to begin with. If it were size or colour intensity alone, I guess there are other gems far cheaper, but which are not diamonds. I'm looking for that event to happen, when everything is aligned.

Oh but is round then the best shape for light return for a fancy cut diamond? Or is another shape better for the sparkly effect that a diamond allows? Do emerald FCDs have any fire?

Being unable to see in person is not a good place to be. As the only explainable example I can give, I prefer the effect of the solasfera vs august vintage rounds, but for a FCD, I would take either. Not sure how this translates to FCDs. So frustrating...

 

[kenny]

Re: Advise on Fancy Diamond Shapes (and high fire coloured g

Cut for light performance is the same for colorless or colored diamonds.
Either the angles send almost all of the light back out the top or it lets it leak out the sides and bottom.
The body color of an FCD has no effect on this as far as I know.

The proportions can help or hurt the light performance in white or colored diamonds
It is usually done poorly for white diamonds but today there's a growing market for well cut whites.

In the FCD world a customer wanting good cut for light performance is on her/his own.
That is not the priority for cut.
Maximizing color and profit is.

You are like me; I also want the best of both worlds.
It is one reason I have returned 6 FCDs.

Buy from a vendor with a good return policy.
One idea if you have the credit limit is to buy a few and send all back but the best one.

I think round IS potentially the best shape for light return since all 8 section are supposed to be placed symmetrically around a central axis just like the parabolic reflecting mirrors used in some of today's high-tech telescopes and radio antennae.

Still this theoretical advantage of rounds does us no good if the round is not cut well - and again cutting to amp up the color and save weight is the priority in the FCD world.

There would be nothing wrong with using an Idealscope on a colored round or an ASET scope on any other shape.
Emeralds can have nice fire when the proportions are good, and again they have the largest facets for the biggest flashes of fire.
Use the same guidelines as with white diamonds.

 

[TristanC]

Re: Advise on Fancy Diamond Shapes (and high fire coloured g

Thanks for the help so far Kenny. I suspect then the reason why almost all the rounds I see have deep pavilions is to enhance the colour of the gem?

Leibish's rounds seem to be cut deeper than 61, with a large percentage running into the 62 and above range.

The tables are also larger than 60 frequently. Do you have the depth and table measurements for your gorgeous green round?

Princesses seem extremely rare out of all FCD shapes. I hardly see any at all.

What do you think about the colouration and cut of these 3 stones?

http://www.fancydiamonds.net/view_diamonds/5095.htm

http://www.fancydiamonds.net/view_diamonds/4923.htm

http://www.fancydiamonds.net/view_diamonds/3431.htm

Appreciate your taking a look with your FCD trained eyes

 

[kenny]

Re: Advise on Fancy Diamond Shapes (and high fire coloured g



It's depth is in that spec table in my FCD thread but it really never registered in my mind how deep it was till now.
The GIA report says my F.I. Green is 67.4% deep and the table is 55% with a slightly large culet and a thick to very thick faceted girdle.
Also unlike today's modern brilliant rounds it has a huge bulging high crown, as you can see in the side view above.
I think mine is useless for comparison because it is not a modern round brilliant cut, which is what you are looking at.

It is more like an Old European Cut and I have no idea if they were supposed to be that deep back then.
Plus if the culet was not there and it came to a point it would have been even deeper for the existing pavilion angle.
All I know is it it has wonderful light performance, and again FCDs are frequently cut deep for better color.
My emerald cut Fancy Deep Purplish Pink is 83.6% deep.
It does not have great light performance but I don't care on this one.

Since you are not likely to encounter another OEC FCD I'd ignore the proportions of my green round.

BTW here's a sneaky way to get a good ballpark idea of a rounds proportions:
Use your computer to blow up a side view pic of any fine cut like a Brian Gavin Signature cut or an ACA.
Shrink or enlarge it so the depth is the same as any round FCD you are considering buying.
Then, if you have it, use software to overlay one on top of the other.
Or you could just print them both on paper then place one over the other against a bright window, lining up the culet and tables.
This lets you see if the round FCD you are considering has the proportions of a know well-cut round.

Of all 3 you posted I like the middle one the best by far.
That color.

 

[TristanC]

Re: Advise on Fancy Diamond Shapes (and high fire coloured g

Totally with you on the colour. But it is to be set, so... size matters