Thicker or thinner arrows and the other 42 facets in a diamond

[dyemonds2002]

Which are better to buy thicker arrows or thinner arrows which one is true H&A also I am curious why the other 42 facets in a diamond are not talked about only 16 are could this explain why light leakage and light return can be affected by not knowing the rest of the facets they are all important not just knowing crown and pavillion angles and girdles etc. Can someone explain.

 

[valeria101]

Not sure I am getting this right: how about the H&A logos on the "Pricescope True Harts and Arrows" doc? (HERE) and grading standards (HERE).

Which facets are not involved in the formation of the harts and arrows as explained down the link above?

There does not seem to be much is any variation in the thickness of the arrows among these "true H&A"... Can you give us an example of what 'thin arrows' would be?

 

[dyemonds2002]

That is exactly what I am talking about the thinner arrows do not perform as well as the thicker arrows every single facet in a diamond should be looked for in light return and leakage if every facet was examined and was perfect then we would have a perfect diamond not just crowns and angles and depth and tables and girdles but instead we should examine kites and other facets in a diamond for perfect light return. HCA and Sarin does not explain it all need more numbers

 

[valeria101]

There is good light return beyond the H&A limts: the pattern is more linked to cut parameters and symmetry, but light return is posible beyond the strict limits required for the harts and arrows to form. This is what the Ideal Scope 'reference chart' tries to show.

I am not sure wether the light return of the very best H&A can be matched by stones with no harts or arrows and otherwise desirable proportions, but beside the outmost extraordinary, harts and arrows may not be an absolute requiremet for top light return.

Also, the H&A pattern insures not just light return but contrast, fire and scintillation: the non H&A may excell in just some of these more subtle cathegories making up optical performance.

Besides, thin arrows like that are no longer in line with the standard for the "H&A" denomication at all.

If you really want a complete virual representation of the diamond with all cut details included, maybe an OGI report and DiamCalc would satisfy this demand. However, no simmulation is without error, and direct analysis on the stone is probably the only thing precise enough to tell apart the best among H&A stones. I am not sure the abriged Sarin reports and the HCA are suposed to go that far, by design.

Just my 0.2, of course.

BTW: is this a theoretical chat? It is always easier to talk about a certain stone... I supose.

 

[Garry H (Cut Nut)]

Fraid it is a bit more complex than that too Ana

H&A's are possible at 25 degree crown angles.
The kite facets Dyemonds are the 8 main facets that et measured.
If a diamond is H&A's that will mean that the symmetry is very tight so you need not worry about aveages and variations.
The minor facets on the crown side play a lessor role than the lower girdle facets. As you rightly indicate - these facets influence the size of much of the firey flashes - but if they get too short = fat then the light return is reduced because the dark star you see is a reflection of your own head. Your head blocking some illumination helsp to make it possible for weaker firey returns to be seen. You can do a search of 'fire is the enemy of brilliance' and read more about that concept.

The other little known fact is that the size of the stars is related to the table size. Big table = skinnier stars.

 

[valeria101]

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On 3/29/2004 3:24:45 PM Cut Nut wrote:


Fraid it is a bit more complex than that too Ana
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"Affraid" is a good word... For some reason, most stones with HCA<2 found with suitable specs in place fall near the Tolkowsky ideal. But this sounds like only a bit of the story, even before your mention of minor facets' play

The range for desirables cuts in the chart of crown and pavilion angle pairs posted in the tutorial is much wider (BIC and FIC included...) and HCA<2 goes beyond even that range. Where are H&A feasible - correctly or not - in this range of measures is not commented on.

And then comes the minor facets' story.

Should PS produce a diamond cut grading course ?

 

[Garry H (Cut Nut)]

This has a 25 degree crown

 

[Garry H (Cut Nut)]

The star looks a little unusual.
But not bad for an AGS 10

The contrast would not be great - but the light return is far better than a normal H&A.

Oh and the spread is that of a diamond with a 10% bigger weight