Switching out my 40.1 pav stone! How much do LGFs matter for 35/40.6?

[candyfloss]

Some people might remember me from a previous thread - I bought a 60/60 style 40.1/34.6 IGI graded round brilliant for an e-ring, way before I knew about this forum and the recommended proportions/grading labs. I really tried to give the stone a chance, but it just didn’t seem to sparkle. Fire was pretty much non-existent. I tried different lighting conditions but it just looked a flat white. It bothered me endlessly. The last straw was when I realised that the stone looked smaller next to a better cut one which in fact measured smaller (in mm). I was dejected.

After much negotiation, my jeweller has fortunately allowed me to switch out the stone. After a rather long search, in which I realised a lot of the stones my jeweller carried had less than ideal proportions, I chose a GIA 3EX with the following specs:
Table: 55%
Depth: 62.5%
Crown: 35.0° (15.5%)
Pavilion: 40.6° (42.5%)
Lower half: 75%
HCA: 0.6 within TIC range, excellent in all except VG spread, looks like average sized

When I was seeking advice/opinions on my 40.1 pav stone, I learnt that longer LGFs would go a long way in reducing obstruction as it makes the arrows thinner, hence helping the stone to not look as dark since these arrows stay dark under more circumstances with such a shallow pavilion.

Given this might not be a “true” 40.6 given the 42.5% (or it may be, depending on the culet but who knows really with GIA rounding so just going with worst case scenario here) is there going to be a perceivable difference between 75 and 80 LGFs? (once again considering GIA rounding)

I feel I have really fallen down the rabbit hole here but since I’m here I might as well find out too - anything else I should note for the above stone? Is 0.6 on the HCA a concern since 1-2 is better for rings? It also seems a touch deep but the crown/pav relationship and table/depth percentages were truly the best I could find after a long and rather exhausting search that I am more than ready to end.

Am I worrying too much and over analysing? I am not looking for a super ideal sort of stone, just something that isn’t a bad GIA 3EX. I am also just really hoping this will be an obvious difference in sparkle from my previous stone and that it will in a way be worth all this trouble and search fatigue. All opinions/help are welcome!

 

[yssie]

Given this might not be a “true” 40.6 given the 42.5% (or it may be, depending on the culet but who knows really with GIA rounding so just going with worst case scenario here) is there going to be a perceivable difference between 75 and 80 LGFs? (once again considering GIA rounding)

Can you elaborate on what you mean here? I don’t quite follow. Does this stone have a larger culet? Why do you fear culet is impacting reporting of other dimensions?

The angles reported on the GIA are measured, not calculated. Then rounded, yes. Pavilion is rounded up to the nearest 0.2degree, using a half-up rounding scheme.

 

[Karl_K]

lgf% 77-78 is probably close to optimal but can handle a bit shorter or longer.

hca has changed a bit with more combos getting under 1 that are fine in rings. This is one of them.

 

[candyfloss]

Can you elaborate on what you mean here? I don’t quite follow. Does this stone have a larger culet? Why do you fear culet is impacting reporting of other dimensions?

The angles reported on the GIA are measured, not calculated. Then rounded, yes. Pavilion is rounded up to the nearest 0.2degree, using a half-up rounding scheme.

Sorry if that wasn’t quite clear! I was actually referencing some of the threads I’ve read. It seems that even though the culet may be reported as “none”, it could in fact be really really tiny, and even that tiny amount is enough to throw off calculations and cause the pavilion depth to be rounded down to 42.5% instead of up to 43%. If the culet were truly zero, a true 40.6° pavilion would translate to 42.8%, which would be rounded up to 43%. Since there is no way to know if the culet is zero or otherwise, there is a concern that the pavilion angles on this diamond might be a touch shallow and enter the 40.5° range.

 

[candyfloss]

lgf% 77-78 is probably close to optimal but can handle a bit shorter or longer.

hca has changed a bit with more combos getting under 1 that are fine in rings. This is one of them.

This is good to hear thank you Karl!

 

[yssie]

Sorry if that wasn’t quite clear! I was actually referencing some of the threads I’ve read. It seems that even though the culet may be reported as “none”, it could in fact be really really tiny, and even that tiny amount is enough to throw off calculations and cause the pavilion depth to be rounded down to 42.5% instead of up to 43%. If the culet were truly zero, a true 40.6° pavilion would translate to 42.8%, which would be rounded up to 43%. Since there is no way to know if the culet is zero or otherwise, there is a concern that the pavilion angles on this diamond might be a touch shallow and enter the 40.5° range.

Ah - now I understand what you’re referring to. Angle is always better than percentage, when you’ve got it a because it is measured (in stone scan), not calculated.

 

[yssie]

I’ve looked through your old threads.

Can you post the full plot diagram or list of measurements for your current stone? Don’t leave any of them out. If you have any photos or videos, post them as well. Don’t bother posting HCA screenshots. Please also share colour and clarity, fluorescence, and inclusion diagram or list of inclusions in the order listed on the report if there’s no diagram for your stone.

Your observation that your current stone both looks smaller and doesn’t show fire... Makes me wonder if there isn’t something else going on with it. All else okay, a overly shallow pavilion will create over-obstruction up close (too many facets turning black), but it should show plenty of coloured dispersion from arm’s length and when tilted. And all else okay, your stone should look bigger than PS preferred variants.

First step here needs to be to figure out what’s actually going on with your current stone. That will determine what to look for in an exchange.

 

[candyfloss]

Appreciate your help with this! The current stone is a D, VS2, no fluorescence, inclusions: crystal. No plot diagram from the IGI certificate. It looks a bit yellow in photos for some reason but it was very white in person.

The loose diamond photos were taken under jewellery shop lighting. I’m not sure if I’m conveying this right, but it just didn’t seem to show end to end brightness once out of the store - the edges would turn dark. Have also included some photos of it after it was set, sorry for the terrible quality I need a new camera!

 

[yssie]

When you say "edges would turn dark" - is this what you're referring to? As in, the edges of the stone showing big black paddle shapes like this?

 

[candyfloss]

Yes! I tried tilting the stone and experimenting under different lighting conditions and did manage to see the other paddles “light up” in one variation or another. The corner at 5 o’clock seemed particularly stubborn though and would remain dark a lot more often than the other corners.

 

[yssie]

Okay! So yes. You are referring to over-obstruction, not something else.

What you’re seeing is the direct result of an overly shallow pavilion and crown combo. Think of each facet as a mirror. When you look in the mirror, if the mirror is directly facing you, you see yourself. If the mirror is tilted a bit, you still see yourself, plus a bit of whatever is beside you. If the mirror is tilted a lot, you see what’s beside you - you don’t see yourself in it at all. If each facet is a mirror, and you are leaning over the stone, then “you” are actually a pretty dark, shadowy blob... In overly shallow stones too many facets are reflecting the dark shadowy you-blob all at once, creating those paddles, even as you rock the stone (ie. Tilt the mirrors a bit). In a more traditionally-proportioned stone fewer facets will reflect the shadowy you-blob at one time, and you’ll have to tilt the stone less to make those facets reflect what’s beside you (your brighter environment).

Unfortunately, thanks in part to the rounding and averaging that you brought up in your original post, the proportions you list in your original post may also yield a stone that has this same over-obstruction problem. It may not. These proportions are kind of on the fence of being just fine. If it does show this issue, it shouldn’t be nearly as severe as your current stone, but you’ll want to spend some time with it before committing, to ensure it suits your tastes. Have you seen it in-person yet?

 

[Karl_K]

40.6 gia numbers is very often just fine.
Do you have any images?

 

[candyfloss]

I like the dark shadowy blob explanation makes perfect sense! A photo below, I haven’t yet seen the stone in person!

Issues with symmetry at 8-10 o’clock, definitely not going to be a hearts and arrows stone but am okay with that given my current one isn’t terribly symmetrical to start with as evidenced by the scope images. It was either this or steep-deeps or more shallow pavilion stones so I figured I’d rather take a slight symmetry problem over that. The stone also seems slightly tilted downwards in this photo but I’m not sure if I’m imagining things.

 

[Karl_K]

photo is inconclusive.

 

[candyfloss]

Thanks for taking a look @Karl_K! What would a conclusive photo be like? Would it show dark paddles around the arrow heads or perhaps in the table itself?

 

[sledge]

Perfect 40.6 pavilion with perfect 0% culet:
50*tan(40.6) = 42.86%, rounded to 43% on GIA report

Perfect 40.6 pavilion with 0.003% culet (shown as "none" on GIA report):
50*(1-0.003%)*tan(40.6) = 42.727%, rounded down to 42.5% on GIA report

The caveats being:

1. Culet is measured at 10x, so minor rounding may be occurring that creates a teeny tiny culet that is still being reported as none on the report.

2. Safe to assume the reported GIA pavilion angle of 40.6 is not perfect. You have to factor in GIA gross rounding which takes 8 actual pavilion values and condenses to a single averaged value that then gets rounded to the nearest 0.2 degrees.

3. A reported value of 40.6 can actually mean anything between 40.5 to 40.6999. If on the lower side of 40.5 and no culet, the pavilion depth comes out to 42.704%, which gets rounded down to 42.5%. If by chance the stone had a 0.003% actual culet & 40.5 pavilion, the percentage pulls down to 42.576% which would also be rounded to 42.5%.

 

[candyfloss]

@sledge to the rescue, exactly what I was talking about when I was concerned the pavilion angle might be lower than 40.6 given the 42.5% pavilion depth! Since the cliff where over-obstruction becomes an issue is at 40.45, am hoping we will still be above that for this stone, but as you said, with an averaging of 8 facets, it is hard to tell without a more exact measurement like a sarin.

 

[sledge]

Nerd talk aside, it appears the proportions of the new stone would put you in an overall better position than the old stone, even if it isn't perfect and has a little obstruction.

What I dislike is the assymetry from the 2 and 7-10 o'clock positions of the new stone. The photo does look tilted to me and I suspect is causing an over exaggeration but I am guessing there are still some issues.

Is your jeweler local? If so, can you go inspect the stone in-person? Check for obstruction issues and also the symmetry. I might also bring an ASET to check light performance. Not sure who did the H&A images of the old stone, but it may be nice to have them done on this new stone as well (requesting they try not to tilt them like they did on the old ones). Lastly, if not local, perhaps a video showing up close and normal lengths away from the viewer in an attempt to replicate obstruction.

Is the limitation of steep-deeps, even more shallow or this stone alone a function of dollars or simply your jeweler's lack of inventory? Asking because maybe it's worth a few bucks more to find something not on the fringe? Not that I think a 35/40.6 is bad, but because you seem "snake-bitten" and wondering if getting you to a safer area would put your mind at ease.

Forgot to mention earlier, don't forget that LGF's are also rounded, except to the nearest 5%. So a 75 reported value can mean anything between 73-77, just as an 80 can mean anything from a 78-82.

 

[candyfloss]

Yes my jeweller is local! I will be going down to view the stone in person once it arrives and deciding whether to keep or reject it. They will be providing the heart and arrows scope for me to view those for myself, though as far as I know they do not have an aset scope (neither do I unfortunately). Agree on the symmetry issue too, will have to check and see how bad it is in person!

In terms of checking for obstruction, would I have to do so away from jewellery store lights? I.e. will those blinged-out lights just flood the stone with so much light that any obstruction is masked? I will be checking to see how it looks close up and half an arm’s length away. Snake-bitten is definitely accurate after my previous stone, so any further tips for checking are much appreciated!

The limitation is due to my jeweller’s inventory. I kid you not that this was the best crown/pav relationship I could find, it is sad but true. I regret that I didn’t realise how limited and bad their inventory was until it was too late and I would hate to throw good money after bad but they aren’t actually charging me anything other than any increase in the price of the stone itself to change it. They have also agreed to remake the setting to ensure it fits the new stone I choose, hence I decided to stick with them instead of going somewhere else. The deal was however that I must choose from their inventory, instead of bringing a new stone in from somewhere else (else I would likely have already run off to JA, WF and the likes to source for a better/safer stone…)

 

[sledge]

Jeweler's lighting is designed to showcase stones, even bad ones. I would definitely ask to check the stone out in as many lighting conditions as they will let you. Back office under normal lighting, outside in indirect lighting, etc.

Put it through the ringer. Try to replicate all those conditions where you saw obstruction in the original stone.

I agree the jeweler seems to be working hard to keep the deal intact. However, if you aren't happy with any of the solutions offered then it's worth considering a refund. Does your paper work clearly define their refund policy? If not, it may be worth an ask. I'm sure they don't want to lose the business, but maybe losing a minimal amount now is better than living with a stone you don't love for years to come and then upgrading X years down the road and feeling like you threw all that money away instead of a small percentage.

I'm not encouraging you to walk, but rather to consider all your options. Being fairly recent, you may still have some options, whereas those options will dissipate as time passes.

 

[candyfloss]

Thanks for the suggestions, going to try to see if I can view it under different lighting conditions and if it can be mounted on a temporary holder while I give it a whirl!

The setting while simple is unfortunately seen as customised as I wanted a thinner band than they were offering, hence there’s no refund on that. As for the stone, I can upgrade it to one 2x the value (not a great policy as compared to say WF’s, as I have come to realise a tad bit too late). But that’s pretty much it.

I definitely see where you are coming from though, having wrestled with a non mind clean stone. My backup option if all fails and this new stone doesn’t fit the bill would probably be to keep the stone for now and have it reset into a pendant someday. That would however mean wasting the setting, so truly hoping I have found the one in this stone and I don’t have to take this path!

 

[sledge]

How many days has passed since the original purchase?

Also I am unclear. One post you said your swap was limited to inventory he had on-hand. In another you said he was shipping the stone in eluding he was using a virtual inventory where there are likely many more choices, which made me think the color, clarity and carats you are seeking is tough to fit in the established budget.

On a side note, does the new proposed stone have fluor, and also what is the girdle thickness?

 

[candyfloss]

About 2.5 months since I first paid for it given it took 1.5 months to make the setting and set the stone, and I was trying to love it for another month.

Sorry for the confusion! What I meant was that I could only source from within the options on my jeweller’s website. I’m not sure how those stones become options? But basically once I select one, it will then be shipped here for me to have a look at. I’ve asked if they can source from say the same database as JA, but they’ve said that is not possible.

The new stone has no fluorescence, but a slightly thick girdle!

 

[yssie]

Yes. Stone is tilted down toward 7 o'clock. And yes, optical symmetry is imperfect.
It'll be better than your current - on the over-obstruction front.

When you visit it in-person, take a full-sized notebook or a couple of A4 sheets of white cardstock. You can use them to shield the stone from the spotlights - the way the stone looks in the shadow is a decent visual of diffuse lighting behaviour. And wear a dark shirt and a dark mask, and let your hair down, and you'll get some idea of worst-case obstruction.

 

[Karl_K]

Thanks for taking a look @Karl_K! What would a conclusive photo be like? Would it show dark paddles around the arrow heads or perhaps in the table itself?

well that would be conclusive not to get it in that case.

In this case the stone is tilted 2 different ways and the lighting is wacky but how wacky is unknown.
In order to properly interpret these photos you have to first at least roughly interpret the lighting and tilt.
In this case in my opinion that is not possible to reach a point I'm comfortable giving an opinion.

 

[candyfloss]

When you visit it in-person, take a full-sized notebook or a couple of A4 sheets of white cardstock. You can use them to shield the stone from the spotlights - the way the stone looks in the shadow is a decent visual of diffuse lighting behaviour. And wear a dark shirt and a dark mask, and let your hair down, and you'll get some idea of worst-case obstruction.

Thank you for the advice! I usually dress in black and I have dark hair as well so I will be sure to be my normal self and throw on a black mask for good measure I’m a bit worried about the symmetry but will see how it looks under the H&A scope before deciding!

 

[sledge]

About 2.5 months since I first paid for it given it took 1.5 months to make the setting and set the stone, and I was trying to love it for another month.

I'm assuming the time period for returns would have kicked off when you picked up the completed ring, roughly a month ago. You are likely beyond or very close to an expiration period to return. If you decide to explore this option, you should do it sooner rather than later but it may already be too late.

For reference, WF is pretty generous and has a 30-day return policy on their in-house stones (ACA, ES & PS). Their virtual inventory stones are limited to a 10-day return period.

It sounds like your jeweler is using a virtual network so I'm guessing he may have a similar 10-day return policy.

Sorry for the confusion! What I meant was that I could only source from within the options on my jeweller’s website. I’m not sure how those stones become options? But basically once I select one, it will then be shipped here for me to have a look at. I’ve asked if they can source from say the same database as JA, but they’ve said that is not possible.

It sounds like your jeweler has a relationship with one or more virtual suppliers and he wants you stay within that network. Totally understandable. Some of the stones on JA may also be in his network but because JA blocks report numbers it would be difficult to confirm that. WF virtual inventory stones may also overlap, but their branded H&A stones (ACA, ES & PS) would not be in the virtual network.

Do you mind sharing your jeweler's website? Perhaps we can search and find a better alternative? Probably a long shot. Just trying to give you a better option is all.

 

[candyfloss]

well that would be conclusive not to get it in that case.

In this case the stone is tilted 2 different ways and the lighting is wacky but how wacky is unknown.
In order to properly interpret these photos you have to first at least roughly interpret the lighting and tilt.
In this case in my opinion that is not possible to reach a point I'm comfortable giving an opinion.

Indeed forgive me I could not think of an example where it would be conclusive to get it, barring something like WF’s excellent photos I shall have to go and have a look for myself then! We shall see exactly how wacky that tilt is, stone does look a tad bright as well. Contrast looks good though (at least to me), save for that 1 o’clock arrow which I’m not sure why is bright

 

[candyfloss]

Really appreciate your help @sledge! Unfortunately I’m actually not in the US (currently based in Asia for work) so my jeweller is small and probably easily recognisable. Well cut stones just seem so hard to come by here, people tend to trust the grades on certificates and would rather go for high colour and clarity, even my jeweller is probably frustrated with these cut proportions I keep insisting on!

Thanks for explaining about how they might be working with a few virtual suppliers, this makes sense! I just wish they would have picked better ones… but again I don’t think people here are that aware of proportions, a GIA 3EX is considered amazing as is. And yes can’t say I’m particularly glad about how JA blocks report numbers and makes you request certificates to view them now. But let me check in about this return policy! I think I’m probably past the window, but no harm checking really.

 

[sledge]

Looking back over your other threads, this might tick your check boxes.

GIA 3X 0.78 E-VS1 @ $2,975

https://diamonddealfinder.com/enquiry.php?id_field=3109270

No pics or videos on this particular vendor's website, but has promising proportions. Share the GIA report number and see if your jeweler has access to this stone. If so, maybe it's worth also bringing in for a look. Obviously, the price your local jeweler charges may be different than the online vendor I found, but it should give you a reference point.