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Marquise - selecting best light performing stones

S

SJL

Rough_Rock
Joined
Apr 27, 2024
Messages
9
Hi all

I am getting a ring designed at a local jewelers. It will have a 0.4 - 0.5ct marquise diamond.
Once they provide me with some stone options, how do I ensure that I am choosing the best stone in terms of sparkle etc?
(They did show me a couple options but I didn't feel 100% and i've decided to go slightly larger. I am waiting for some more slightly larger stone options).
They will send me videos, but I don't think they have aset scope images.

I tried going onto James Allen's website and putting different depth and table dimensions in (to give me an idea) and I felt there were good and bad in each category.
Are table and depth really that reliable for marquise?

Any advice appreciated!
 
SJL said:
Hi all

I am getting a ring designed at a local jewelers. It will have a 0.4 - 0.5ct marquise diamond.
Once they provide me with some stone options, how do I ensure that I am choosing the best stone in terms of sparkle etc?
(They did show me a couple options but I didn't feel 100% and i've decided to go slightly larger. I am waiting for some more slightly larger stone options).
They will send me videos, but I don't think they have aset scope images.

I tried going onto James Allen's website and putting different depth and table dimensions in (to give me an idea) and I felt there were good and bad in each category.
Are table and depth really that reliable for marquise?

Any advice appreciated!
Click to expand...

In a word, no. I think it does help to narrow it down some but like you said, you will find good and not-so-good stones in and
out of range. You really have to use your eyes and watch how the facets turn on/off as the stone rotates.

You may also try looking for Excellent under Polish and Symmetry. (Symmetry will often only be Very Good for fancy cut stones.)
I tend to think that the cutter thought it was a good enough stone to spend a little extra time on it but whether this is reflected
in the beauty of the stone is still questionable.

You may have also noticed that marquise come with different numbers of mains (on the pavilion). In my observation,
most have 8 mains with the split at the center (causing what most people call the bow-tie effect). Others are 6 mains with the
arrows (mains) going straight through the center. There are also 4 mains which tend to have a little chunkier faceting. None
is better than the other. Just different flavors.

8 main example
6 main
4 main

Good luck!
 
tyty333 said:
In a word, no. I think it does help to narrow it down some but like you said, you will find good and not-so-good stones in and
out of range. You really have to use your eyes and watch how the facets turn on/off as the stone rotates.

You may also try looking for Excellent under Polish and Symmetry. (Symmetry will often only be Very Good for fancy cut stones.)
I tend to think that the cutter thought it was a good enough stone to spend a little extra time on it but whether this is reflected
in the beauty of the stone is still questionable.

You may have also noticed that marquise come with different numbers of mains (on the pavilion). In my observation,
most have 8 mains with the split at the center (causing what most people call the bow-tie effect). Others are 6 mains with the
arrows (mains) going straight through the center. There are also 4 mains which tend to have a little chunkier faceting. None
is better than the other. Just different flavors.

8 main example
6 main
4 main

Good luck!
Click to expand...

Excellent advice.
Ask for ASET image if they can get it.
 
tyty333 said:
In a word, no. I think it does help to narrow it down some but like you said, you will find good and not-so-good stones in and
out of range. You really have to use your eyes and watch how the facets turn on/off as the stone rotates.

You may also try looking for Excellent under Polish and Symmetry. (Symmetry will often only be Very Good for fancy cut stones.)
I tend to think that the cutter thought it was a good enough stone to spend a little extra time on it but whether this is reflected
in the beauty of the stone is still questionable.

You may have also noticed that marquise come with different numbers of mains (on the pavilion). In my observation,
most have 8 mains with the split at the center (causing what most people call the bow-tie effect). Others are 6 mains with the
arrows (mains) going straight through the center. There are also 4 mains which tend to have a little chunkier faceting. None
is better than the other. Just different flavors.

8 main example
6 main
4 main

Good luck!
Click to expand...

Thank you so much for your response!
I really appreciate it.
 
A point on symmetry and polish. @tyty33 mentioned cutters cutting corners.
Infact it's a bit more complex.
Here are some snippets from my upcoming book - should be published July:

The table below supports the fact that most round brilliant cuts that GIA
grades receive its top cut quality grade. I would prefer a higher standard for
round diamonds because better symmetry is vital for round diamonds and
easier to achieve than for many fancy shape diamonds. For round diamonds,
a stricter symmetry grading system would serve consumers better. Perhaps
an ‘Ideal’ grade above excellent?
1715522953872.png

Achieving better symmetry and polish for round diamonds is easier, and
more important, than for many fancy shape diamonds. Polish quality is
easier to achieve for rounds because of the morphology of diamond crystal
hardness variations.
Symmetry is vital for rounds because the eight main facets on the crown and
pavilion must act as opposing mirrors directing incoming light in and out
with little internal ‘bouncing around’. Very few facets on fancy shape diamonds
are directly opposite each other and as a result light tends to bounce
internally before emerging. This is the main reason that round brilliant cuts
are more brilliant than fancy shape diamonds.
You can’t polish a diamond within the same plane as its natural crystal faces.
The perfect diamond crystal boasts an octahedral shape, resembling a pyramid
balanced on an inverted pyramid, which comprises eight equilateral
triangular faces.
These faces are depicted in the crystal image on the right from the earlier
discussion, regarding crown and pavilion angles. Furthermore, these faces
serve as cleavage planes. When an attempt is made to polish them, layers
can easily slough off, which makes achieving a high polish an insurmountable
challenge.
In certain instances, some pavilion facets extending from the girdle on some
fancy-shaped diamonds closely approximate, if not precisely match, this
crystal face angle of 54.74°. This angle is 14 degrees steeper than the steepest
facets found on well-cut round diamonds.
On occasion, a compromise must be struck – the cutter must decide between
accepting subpar polish or adjusting that facet’s tilt and thus reducing the
symmetry grade. Opting for the latter choice, pursuing an improved polish,
is usually the wiser decision.
Poor polish can be on every facet if the diamond was polished on an old or
damaged scaife (polishing turntable). More often, however, there will be one
facet with a lizard skin effect seen under magnification. Occasionally crystal
twinning or graining hardness variations can cause ripples in a facet surface
also resulting in a polish downgrade.
 
Thanks, @Garry H (Cut Nut) for the above info. I had no idea so much went into the polish/symmetry decision. Good stuff!
 
tyty333 said:
Thanks, @Garry H (Cut Nut) for the above info. I had no idea so much went into the polish/symmetry decision. Good stuff!
Click to expand...

Loads more in the book.
Will be handing out some pre print promo's at the Vegas show :-)
Foreword by none other than John Pollard - proofing by Karl Storm Rider
 
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