GemAdvisor file generation for 2 stones

[vanquish]

Hi

Would it be possible for a fellow PSer to generate 2 .gem files using DiamCalc so that I can make an estimated comparison of 2 stones? I understand that the data provided below is rounded and averaged and that the stones won''t be perfectly symmetrically cut, however, I would like to get an impression of how the different proportions and particularly table size and girdle thickness might affect potential appearance. The stones are

1

Depth: 60%
Table: 56%
Crown Angle: 33.5
Crown Height %: 14.5
Pavilion Angle: 40.8
Pavilion Depth%: 43
Star Length %: 55
Lower Half %: 75
Girdle thickness: Medium 3%
*Carat Weight: 1.01
*Diameter: 6.5 - 6.6 (for the purposes of making the DiamCalc model generation more simple, 6.55 can be used if this figure is needed)


2
Depth: 61.1%
Table: 60%
Crown Angle: 34
Crown Height %: 13.5
Pavilion Angle: 40.8
Pavilion Depth%: 41
Star Length %: 50
Lower Half %: 80
Girdle thickness: Thick 4.5% (report is slightly thick to thick)
*Carat Weight: 1.00
*Diameter: 6.4

I realise the time that will be invested in doing this, so I''m very grateful if anybody can help.

 

[vanquish]

Sorry

I forgot to give depth measurements (now added). Total stats available are now

1
Diameter: 6.5 - 6.6 (for the purposes of making the DiamCalc model generation more simple, 6.55 can be used if this figure is needed)
Depth: 3.93mm
Depth %: 60%
Table: 56%
Crown Angle: 33.5
Crown Height %: 14.5
Pavilion Angle: 40.8
Pavilion Depth%: 43
Star Length %: 55
Lower Half %: 75
Girdle thickness: Medium 3%
Culet: None
*Carat Weight: 1.01

2
Diameter: 6.4mm
Depth: 3.91mm
Depth %: 61.1%
Table: 60%
Crown Angle: 34
Crown Height %: 13.5
Pavilion Angle: 41
Pavilion Depth%: 43
Star Length %: 50
Lower Half %: 80
Girdle thickness: Thick 4.5% (report is slightly thick to thick)
Culet: None
*Carat Weight: 1.00

 

[stone-cold11]

It doesnot really solve the problem with symm. These are average numbers, with the geometry of the stones not included, so a Diamcalc simulation is going to be the best case scenario. Unless you can get a full sarin scan of the stone, with the numbers for each facet, doing a Diamcalc simulation will be useless, garbage in garbage out.

 

[Lorelei]

It would be best if you could get actual Idealscope or ASET images for each diamond, these would reveal far more. Both diamonds look promising by the numbers, the second has a larger table so this is down to a matter of taste.

 

[Paul-Antwerp]

Something is incorrect in the measurements of the first stone. Which lab graded these?

Stone and Lorelei are correct in their advice, by the way: averages are not the same as the actual stone.

Live long,

 

[vanquish]

Hi guys

Thanks for the feedback; I appreciate your views. I know that the images generated would be idealised estimations only. However, as I am not able to get ASET or idealscope images for either stone, this is the one of the only options open to me to understand the differences before committing. I am particularly interested in seeing can I notice the difference between a 60% and 56% table, idealised effects of the different proportions and also what effect the thick girdle has?

Having done quite a thorough search on past posts, I am aware that GIA use an rounding and facet averaged process to generate the spec and that the SARIN equipment itself has measurement tolerance of ~0.2deg. As stone #1 is only good for symmetry, I realise that a DiamCalc simulation using these average numbers will not give a result that matches the stone in practice. As an engineer I know where you are coming from with the "garbage in garbage out" statement as it applies to all CAE packages; however, I believe that simulating the stones still can provide useful insights on a high level regarding the makeup of the stone once the person analysing the images is aware of the approximations that were made (I am not expecting the stones to perfectly match the simulations, but it will provide a best case comparison between the 2).

Paul - GIA graded the stones; the first stone is only good for symmetry (might this explain the problem?) What problem are you seeing in the measurements?

Please, if anybody can run this simulation for me, I''d be so grateful.

 

[stone-cold11]

This thread might be useful to you. Shows you the images for different parameters.

http://journal.pricescope.com/Articles/72/1/Laboratory-Cut-Grades-What-the-report-doesn%E2%80%99t-show.aspx

 

[stone-cold11]

Another.

http://www.goodoldgold.com/Articles/GIACutGrading/Grade1/

Basically, you can infer from all the images in the above 2 articles about the 2 stones'' characteristics. Not really need a simulation unless you have the exact information.

 

[Paul-Antwerp]

The various depths do not seem correct, according to me, vanquish.

 

[vanquish]

SC - Thanks, I hadn''t seen that second article, which does give an impression of the differences in table size. As parametric based indicators, they do provide some insight into the differences I could expect, but none show what I could expect of a thick girdle. I understand the reasons why you would be reluctant to use DiamCalc simulations for this comparison, but I still believe that they will go further than the linked articles to indicating the differences between the stones and I am aware that they will not be representative of the stones in practice. I am aware of the assumptions (idealised symmetry) that would be used to generate the files/images and so think there is value in reviewing them if you or one of your other knowledgeable colleagues could spare the time to generate them.

All - I would really love to be able to see the differences of 2 idealised stones in a DiamCalc simulation before making my decision; I realise the time that needs to be invested in creating the sims and apologise for the inconvenience this would cause. Perhaps somebody could help with this one last step towards choosing my diamond.

Thanks

 

[vanquish]

Hi Paul

Sorry, I had missed your reply. I''ve double checked the figures, they are those off the cert.

See below

http://www2.gia.edu/reportcheck/index.cfm?fuseaction=home.showReportVerification&reportno=16222826&weight=1.01

(hope I made that link right)

 

[strmrdr]

I am curious as to why it came down to those 2, there are better out there.
If you give us your color clarity and price preferences we could likely find better.

 

[Paul-Antwerp]

Sorry, Vanquish, the ''error'' probably comes from a combination of GIA-rounding and the average being skewed with the non-roundness of the stone.

 

[vanquish]

Hi Karl / strmrdr

There are a number of reasons why it''s down to these 2

It took months to find the right ring setting style (she''s been very precise about what she wants) and I finally found it in a store. To her the ring style would be the most important but to me it''s the diamond which is why I''ve been annoying the retailer asking multiple times for available stones. After 1 month he''s understandably exhausted!! So the ring is picked and I''ve had a finite selection of stones to choose from.

Second highest importance to her is carat weight, and having looked at the colour and clarity we agreed on I''m at the top of my budget with GIA "very good" cut grade.

All in all, I feel I''ve invested enough time in finding the ring (> 1 year), now the stone (3-4weeks) such that I''m now wanting to pick the best of the two to go into the perfect ring.

I thank you for your kind offer of seeking out some stones but on this occasion I''ll have to pass.

Hopefully, somebody can generate the files (flawed as they are, especially for ring 1) and then I can make the decision.

Thanks

 

[stone-cold11]

So have you seen the stone? Or just buy an Idealscope? Send it to an independent appraiser with the tools and the ability to scan and generate a Diamcalc simulation?

Sorry, I do not have Diamcalc.

 

[Paul-Antwerp]

So, if you are buying in a store, take a look at both and see which one you prefer in real life. No need to fiddle with incorrect virtual stuff.

Compare them side-by-side in multiple light-environments, also under a desk and outside (if possible), and in a box with a dark background (so that light entering from behind does not suddenly become positive).

For the first stone, let the retailer also check the thickness of the girdle at its smallest point, because there is probably a very thin area.

Live long,

 

[vanquish]

Hi guys

Sorry if I''m frustrating you, I do appreciate your help. I haven''t seen the stones. The ring in store already made up is a size N with tension set side stones, I need a size H (UK sizes, sorry). The store does not make the rings itself but uses wholesale manufacturers; so the ring style has been reordered and I have specified that I want to pick the stone from a list of certified stones with reports (not usual practice when purchasing from wholesale manufacturers I believe). So, having reviewed the list, I am down to 2 stones.

I have a connection with said store which means I am getting a heavily discounted price, and as it has the exact ring style I want (by chance, I have reviewed many other stores), I have decided this is the approach I am taking.

In summary, I haven''t seen the stones and won''t be seeing either until one is set in a ring. Whilst not ideal, the best info I can get is certificate data, which is why I am wanting a DiamCalc image so that in addition to what I already understand, I can gain an estimated appreciation for the differences in stone proportions. I hope you understand.

Thanks for your help.

 

[vanquish]

In the absence of DiamCalc software help to generate the 2 .gem files, I''ve been looking for other links to help me understand the differences. I found the following GIA articles regarding their cut grades the most helpful thusfar. Here are the links

1. Estimating cut grade (including 5 pictures within each GIA grade and commentary of each
http://www.gia.edu/diamondcut/pdf/booklet_estimating_cut_grade.pdf

2. Effect of finish, culet and girdle on GIA cut grade (magnified pictures of symmetry, polish, culet and girdle downgraders)
http://www.gia.edu/diamondcut/pdf/booklet_finish_culet_girdle.pdf

3. GIA cut grade estimation tables
http://www.gia.edu/diamondcut/pdf/booklet_cut_estimation_tables_highres.pdf

They have definitely helped me out.

Still, if somebody is still willing to generate the 2 .gem files I''d be most appreciative.

Thanks