Strain Lines

[elle_chris]

How common are they in CVD grown diamonds?

I've noticed a few diamonds in my FB groups that look.. "off", kinda hazy and it's not the clarity. So I saved a pic of a 4ct that looked weird to me, zoomed in, and think I can see the strain lines. Not sure if it's OK to post the pic here though?

So before I go looking for a lab made Pear, I'd like to know if this is very common? And if so, how to avoid it...

 

[DejaWiz]

From my understanding, strain/grain is present in every diamond grown with the CVD method, since it is the nature of the growth method. When a growth cheat is used (rapid start-stop), the resultant diamond rough is highly tinted and the grain layers can be severe enough to cause light transmission issues making the diamond appear hazy/fuzzy, or even cause double refraction, like Moissanite.

 

[Garry H (Cut Nut)]

Strain and grain are different and not always related.
Internal graining occurs in natural and is prominent in CVD diamonds, sapphires and rubies etc and especially in Argyle pink and brown diamonds.
When the growth is interrupted or the mix or available material that is forming an outer layer on a crystal changes, we get growth lines like in a tree, only usually parallel to that crystal growth plane.
If there is a power outage for example during a CVD ion rain storm, and the process restarts - there can be a grain plane. Or the crystal is taken out, repolished and put back in the chamber. thats how I understand it.

Strain is something we use under crossed polarisation to identify HPHT from CVD and natural diamonds.

 

[DejaWiz]

https://iopscience.iop.org/article/10.1088/0953-8984/21/36/364220

Observations on HPHT-Grown Synthetic Diamonds: A Review | Gems & Gemology

Summarizes statistical data and distinctive features of several thousand gem-quality HPHT synthetic diamonds examined by GIA from 2007 through 2016.

www.gia.edu

 

[Garry H (Cut Nut)]

https://iopscience.iop.org/article/10.1088/0953-8984/21/36/364220

Observations on HPHT-Grown Synthetic Diamonds: A Review | Gems & Gemology

Summarizes statistical data and distinctive features of several thousand gem-quality HPHT synthetic diamonds examined by GIA from 2007 through 2016.

www.gia.edu

Very pretty.
001 faces are cube faces or the planes that the crystals grow on
011 are flat CVD crystal edges if you bevelled them off. Dodecahedral which are prominant on HPHT crsytals.
111 faces are the point corners ground away or octahedral faces

 

[elle_chris]

Thanks for the responses.

So if I go with CVD, there's always going to be some grain lines present. If I go with HPHT, there's a good chance of Blue nuance.

Not sure what I want to do anymore.

 

[DejaWiz]

Thanks for the responses.

So if I go with CVD, there's always going to be some grain lines present. If I go with HPHT, there's a good chance of Blue nuance.

Not sure what I want to do anymore.

There's a chance of blue nuance, but not necessarily a high chance. Luckily, it's pretty easy to identify, even if it's undisclosed in the E-F color grades.

 

[monipod]

Thanks for the responses.

So if I go with CVD, there's always going to be some grain lines present. If I go with HPHT, there's a good chance of Blue nuance.

Not sure what I want to do anymore.

If you choose a good vendor, you can avoid both so IMHO, neither are issues worth worrying about that much. I think a good lab with the latest tech will take great care to avoid obvious strains but in most cases, you would need high mag to even see it.

A good vendor will vet your stone and make sure there is no haziness or other issues, just as with a natural stone. As for blue nuance, I've only seen a few posted here at actual size where I've really seen the blue. If you opt for a GHI stone then I would think the nuance wouldn't even be seen to the naked eye.

 

[oncrutchesrightnow]

First choice would be to go with a trusted vendor who would vet the stone. CVD might have stria and/or strain but it does not always affect light performance. Natural diamonds may have it and pink diamonds will often have it and that doesn’t stop people from buying them. If CVD is the right choice for you then don’t let stria / strain stop you. Same with HPHT — I have heard that even with some blue nuance if you look at a LGD alone with nothing next to it the difference is negligible.

Second choice would be to go with a vendor with a simple return policy and then look at the diamond with your own eyes.

 

[elle_chris]

I don't like fluoro. I sold an ideal cut H&A because it had strong fluoro. Blue nuance is something I would definitely notice in real life as I've noticed it in pics.

I think I will stick with HPHT for an Emerald cut (without any post growth treatments), but will just be very careful about the blue.