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What does obstruction look like?

mission1

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Hi everyone. I’ve noticed that now my diamond is set, when I look at it at a very slight angle to the face at arm’s length a black spot appears just off centre. It disappears if I tilt the diamond back again very slightly. Is this likely to be a bit of obstruction, leakage (?), or just something that diamonds do? In all other ways the diamond sparkles and looks beautiful.
 

tyty333

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What shape of stone do you have?
 

flyingpig

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Read about the table reflection and the centre of a diamond.


In short, it is neither leakage or obstruction.
It is due to the lighting condition of your environment and tilt. There is nothing to worry about.
 

mission1

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Read about the table reflection and the centre of a diamond.


In short, it is neither leakage or obstruction.
It is due to the lighting condition of your environment and tilt. There is nothing to worry about.

Ok, thanks flyingpig. I couldn’t see anything in the link specifically about a black spot appearing at certain angles, but I’ll have a google for table reflection at centre of diamond.

I can see the culet when I look straight into the diamond, and the black spot appears just above it when I tilt the ring downwards - it grows larger the more I tilt it down, and smaller and eventually disappearing as I move it back towards straight in my eyeline.
 
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flyingpig

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No, the article does not specifically talk about the black spot in your case, rather general information about the centre and how it reflect light.

The area you are concerned about draws and reflect light from 45 degree angle. An obstruction issue arises when a facet (s) draws and reflect light from 80~90 degree angle, represented by the areas in Blue in ASET (normally the arrows) Therefore, it is not obstruction.

It is not leakage either, because the area simply does not leak light unless seriously and horribly cut (or have a culet)

When you tilt the diamond and see darkness in the particular spot you mentioned, that spot is just pointing at 45 degrees at an area in your room that is not well lit or produce/reflect light.
 

flyingpig

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it grows larger the more I tilt it down, and smaller and eventually disappearing as I move it back towards straight in my eyeline.
You said it. No darkness when face up straight. It is no leakage or obstruction. 100%. It is physically impossible.
 

sledge

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What's the LGF size reported on the GIA report? I was helping someone else the other day and posted the info below.

As @flyingpig pointed out, it sounds like this is a reflection issue.

- Also this stone the largest LGF's of the group at 78. Still within ideal territory, but again, maybe a slight personality change. Numerically larger LGF's provide more skinny arrows tend to produce a little more pin fire white light return in bright lighting environments. Numerically smaller LGF's produce fatter arrows and produce larger bolder rainbow flashes in indirect lighting. As well cut as these stones are, the differences will be minimal and personal preference. At the 80%+ range, you can start to see some table reflection when you tilt the stone.

1576735504712.png

1576735527554.png

1576735556393.png
 

mission1

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sledge

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AV_

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I'd venture to say that this is a reflection of the setting. Not sure.
 

Karl_K

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Something like this?
5degreetilt.jpg
 

Karl_K

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Or this?
 

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  • 5degreetilt2.jpg
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Karl_K

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The pavilion mains for many angle and lgf% and the way its mounted one or 2 of them will go very dark around 5 degrees tilt from obstruction but if you tilt them just a few degrees from strait back the degree it happens is less.
Face up
faceup.jpg
 

Karl_K

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Also what are the rest of the numbers from the report? Or the report number and lab?
 

mission1

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It looks more like a spot than that, but perhaps that's just to my eye from a distance. I'm literally the only person that notices it!

We're away on holiday so I don't have the certs with me - but it's a GIA XXX, very slightly shallow 'on paper' (34/40.6), 75% LGFs, 3.5% girdle, 60.2% depth.
 

Karl_K

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It looks more like a spot than that, but perhaps that's just to my eye from a distance. I'm literally the only person that notices it!

We're away on holiday so I don't have the certs with me - but it's a GIA XXX, very slightly shallow 'on paper' (34/40.6), 75% LGFs, 3.5% girdle, 60.2% depth.

tt sounds like obstruction.
As a diamond is tilted different parts go in and out of obstruction.
 

mission1

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Is it possible to see likelihood of obstruction from the image? When I read up I thought it was - and this looked ok based on that... Screenshot 2019-12-27 at 17.43.52.png
 

Karl_K

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yea its obstruction in the pic the small triangle is caused by slightly twisted lowers at 1 oclock and likely 11 oclock causing obstruction in that virtual facet.
 

mission1

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Ok, thanks. What confused me was that it doesn't matter where I rotate the diamond, the dark spot appears in the same place (i.e. just above the culet/centre as I tilt it downwards). Does that still hold true for it being the obstruction you've identified causing this?
 

Karl_K

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Ok, thanks. What confused me was that it doesn't matter where I rotate the diamond, the dark spot appears in the same place (i.e. just above the culet/centre as I tilt it downwards). Does that still hold true for it being the obstruction you've identified causing this?
yea more than likely.
I wouldnt worry about it to much but if it really bugs you do you have an exchange period?
 

mission1

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Ok thank you. Yes, I’m still within return period.
 

mission1

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This video about cleaning diamonds (at 2:10 onwards) is what I'm seeing - though not as obvious on mine as the vid.

.
 

mission1

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Thanks for confirming @Karl_K . Would you say this has a significant overall affect on the performance of a diamond in terms of light return etc, or is it a more minor issue / characteristic?
 

Karl_K

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Thanks for confirming @Karl_K . Would you say this has a significant overall affect on the performance of a diamond in terms of light return etc, or is it a more minor issue / characteristic?
minor issue
 

mission1

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Thanks Karl. It’s far less obvious than the ring in the video.
 
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