Crown height range

[mor2778]

Hey guys,

I'm doing some research about diamonds and I have some things that still unclear to me.
I hope that this is the place to get the right answers

So, for now I have 2 questions open:
1. I'm not sure I fully understand the Crown Height % calculation, I mean I understood the formula: Crown height % = (avg crown height ÷ avg diameter) x 100 but my question is what are the reasonable range for Crown Height %

2. Same thing about the Pavilion depth. I think it's between 42% ~ 50%, am I right?

Thanks in advance,
Mor

 

[mor2778]

Update from the last minutes, I just noticed that the 42% ~ 50% pavilion depth is only the optimal and not the full range

 

[rockysalamander]

When looking at most diamonds, you'll find the crown angle and pavilion angle more often reported in the web description (while the pavilion depth is in the cert for GIA and AGS), rather than the actual depths.

If you want depth, you just solve for depth in your equation.

When you look at GIA diamonds, here are the ranges we recommend.
table: 52-57.5 (but I really prefer under 57)
depth: 60-62.3 {consider 59.5)
crown angle: 34-35.0 (up to 35.5 crown angle can sometimes work with a 40.6 pav angle)
pavilion angle: 40.6-40.9 (sometimes 41.0 if the crown angle is close to 34)
Lower girdle facets between 75 – 80%
Star facets between 40 – 58%
Girdle thickness between thin and slightly thick
Culet: AGS pointed or GIA none

 

[mor2778]

Crown height is easy to find in order to use the formula but how do I found the diameter in GIA certificate? let's take this one for example 6281809006

thanks!

 

[rockysalamander]

Crown height is easy to find in order to use the formula but how do I found the diameter in GIA certificate? let's take this one for example 6281809006

thanks!

Its right at the top under measurements...there will be a range (here 6.36 - 6.45 mm). That range is narrower the more precise the cut.

I would 100% NOT recommend the diamond you suggested!

 

[mor2778]

Oh xD I just took some random diamond. not thinking to buy it, but thanks!!

 

[sledge]

Attached is an image of the cert you asked about.

On a round diamond, the length (L) and width (W) dimensions signify the diameter. In this case, one measures 6.36mm, and the other measures 6.45mm.

As you will notice, there is a 0.09mm difference. While most diamonds are NOT perfectly round, it does seem odd there is this much disparity in the dimensions. Normally we'd see something like 6.36 x 6.38mm. Sometimes you will see a perfect diamond that would measure something like 6.36 x 6.36mm.

I also marked this certificate up to help you find the other information.

Are you considering purchasing this stone? If so, please do not do so! This is very poorly cut and we can help you find something much, much better.

 

[sledge]

Oh xD I just took some random diamond. not thinking to buy it, but thanks!!

Sorry. It appears @rockysalamander and yourself posted as I was creating my response so we have some overlap.

I'm glad you aren't buying. I'm not sure how you picked this particular stone, but it's almost a perfect example of what not to buy.

 

[Dancing Fire]

Cut grade good?? . It should say "UGLY" cut grade. . This stone "takes the cake"

 

[foxinsox]

Oh yeah - despite what you might reasonably expect from what the words mean in English, good and very good cuts aren’t actually any good at all. You want to look for XXX at the very least and the restricted range within that from the parameters above that are likely to ensure good light return.