Polish on a diamond: can a diamond be re-polished to improve polish grade?

Sometimes a diamond has a grain or growth line that makes it impossible to get a great polish on 1 facet.

Labs try not to give appearance grades - they give ''features grades''.
Often it is impossible to find some of these features on a diamond without a microscope and ideal reflected lighting.

Ask what the feature is that makes a stone ''Good'' - and if it is a ripple on one part of a small facet near the girdle etc - then you may find you have a beauty at a better price.

Date: 5/19/2006 8:29:49 AM
Author: Garry H (Cut Nut)
Sometimes a diamond has a grain or growth line that makes it impossible to get a great polish on 1 facet.

Labs try not to give appearance grades - they give ''features grades''.
Often it is impossible to find some of these features on a diamond without a microscope and ideal reflected lighting.

Ask what the feature is that makes a stone ''Good'' - and if it is a ripple on one part of a small facet near the girdle etc - then you may find you have a beauty at a better price.

Garry-thank you very much.  I am searching for a EC and have been eliminating all without a polish grade of VG or better.............Jim from James Allen said he thought it was limiting and that there wasnt necessarily a visible difference.  Is an appraiser the only one who can assess the overall polish to ascertain why the polish is Good vs. Very Good or excellent?  Why are there so few Emerald cuts with Verg good or Excellent polish?

Jim and an appraiser can all help you.

The hardest facets to polish are close to the octahedra crystal faces - the 4 faces on a pyramid.
Emerald cuts have many facets close to those 4 planes.

Fact of life - because emerald cuts come out of octahedra

Date: 5/19/2006 8:38:33 AM
Author: Garry H (Cut Nut)
Jim and an appraiser can all help you.

The hardest facets to polish are close to the octahedra crystal faces - the 4 faces on a pyramid.
Emerald cuts have many facets close to those 4 planes.

Fact of life - because emerald cuts come out of octahedra

you are losing me--is that the bottom of the stone?

In case Garry doesn't get back to this, octahedra is the shape of the crystal.

Date: 5/19/2006 9:21:58 AM
Author: JulieN
In case Garry doesn''t get back to this, octahedra is the shape of the rough (influenced by the growth of the crystal....?)

oh so what specific facets was he referring to

Getting to that.

This is an octahedron.

Please note that I corrected my previous post...

This is a profile view of emerald.  Ok, so I don't know exactly which facets Garry is talking about, but I'm guessing due to the structure of the crystal, it is hard to polish in a certain plane.

Attachments

emrProf.jpg (18.87 KiB) Viewed 472 times

neat

I think he was talking about the 7 and 8 level of facetsw but I could be completely off here. Just my guess because wouldn''t that area be the most pyramid like?

Oh, actually...ok, so if you look at my octahedron, you will see that there are 8 planes...four perpendicular to four.  So pretty much everything except the table is parallel to those planes.  SO, if I'm reading this correctly, the facets that are hardest to polish correspond with 2, 3, 4, 6, 7

Date: 5/19/2006 9:43:09 AM
Author: JulieN
Oh, actually...ok, so if you look at my octahedron, you will see that there are 8 planes...four perpendicular to four. So pretty much everything except the table is parallel to those planes. SO, if I''m reading this correctly, the facets that are hardest to polish correspond with 2, 3, 4, 6, 7

interesting.  however-while i can see that would be more difficult to polish than say the table................it doesnt really explain why there are fewer EC''s with VG or EX polish than rounds..................they have the most and smallest facets right?

I know that the angles between the poles of an octahedron are 90 and 180.  The incline of the plane in diamond, I don't know, exactly.  However, let's say 45.  The CA of a RB is 34/35, the PA is 40/41.  The culet of a round would correspond to the tip of the pyramid.  You're not going to see a PA any closer to 45.  Those are pretty much the standard angles.  For an emerald, there are many more possibilities of angle combinations, and therefore have a higher chance of being parallel to the plane.

ETA: also,the PA is the same all the way around for a RB.  For a rectangular stone, there is more pavilion angle variation.

Date: 5/19/2006 9:58:15 AM
Author: JulieN
I know that the angles between the poles of an octahedron are 90 and 180. The incline of the plane in diamond, I don''t know, exactly. However, let''s say 45. The CA of a RB is 34/35, the PA is 40/41. The culet of a round would correspond to the tip of the pyramid. You''re not going to see a PA any closer to 45. Those are pretty much the standard angles. For an emerald, there are many more possibilities of angle combinations, and therefore have a higher chance of being parallel to the plane.

ETA: also,the PA is the same all the way around for a RB. For a rectangular stone, there is more pavilion angle variation.

in english please..........

Sorry, English isn''t my first language. 

Sample Helium scan of emerald.

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emrSlopeAng.jpg (60.47 KiB) Viewed 472 times

yikes.  what are you a NASA engineer?

Julie what is your first language if you don't mind me asking?  You do very well!

Vietnamese; I remember preschool was a little awkward at times.  I had the kinks ironed out by second grade.

You sure did!!!!! I have never seen you make a grammatical error!

Most immigrants have far better grammar than native born Americans.

No. 6 is the closest to the plane of the natural octahedron..., but all emeralds are cut differently...

Date: 5/19/2006 2:55:05 PM
Author: codex57
Most immigrants have far better grammar than native born Americans.

That is a ridiculous generalization.

thanks JulieN

very well explained

Date: 5/19/2006 5:15:39 PM
Author: Garry H (Cut Nut)
thanks JulieN

very well explained

garry --i appreciate your input as well!

Date: 5/19/2006 4:53:45 PM
Author: windowshopper

Date: 5/19/2006 2:55:05 PM

Author: codex57

Most immigrants have far better grammar than native born Americans.

That is a ridiculous generalization.

Well, technically due to his lexical error, but I think codex57 means to say many immigrants have far better grammar than many native-born Americans. Thanks to immigration requirements, I dare say many know our history and government better as well.

I learned Spanish in High School and College and my Spanish grammar (and spelling) is superior to that of most Spanish/Mexican natives I meet. In fact, learning Spanish at an older age than English actually re-taught me English grammar as well. I attribute this to the fact that when you learn a language as an adult, you learn explicit rules, whereas learning as a native tongue, you learn implicitly, which leaves room for error.

Oh, that and the fact that being gramatically correct is far nerdier sounding to natives. No offense, JulieN, you blend well with your idioms ("kinks ironed out"). I, on the other hand, sound full-blown nerdy even in my native tongue.

We now return you to your regularly scheduled thread.

I was wondering the same question about polish, and figured that maybe polishing a stone once the proportions are correct removes some material and screws up the measurements and such. Maybe that''s way off.

^

I think the thing is as Garry said if there is a grainline the diamond is graded on that specific as the polish will not perhaps be better than good.  A surface grainline would run through the whole diamond, so polishing the surface would not eliminate it.

With an Emerald cut there is less waste from the original rough so the diamond is cut closer to the original exterior of the rough. A round has more waste if you think of the bottom of a pyramid as the widest point where the girdle is then think of a round circle inside a square the corners need to be cut off, with the emerald cut it is not like that.

JulieN,

Just a note to say I enjoy reading your posts -- consistently some very thoughtful stuff for someone who claims to not have any industry ties. Of course there are many other "pro-sumers" out there whom I enjoy reading as well (too many to list), but I''ve especially enjoyed your posts of late and I''m glad you''re part of this forum.

Cheers!

Bill Scherlag

Thanks, Bill!

Date: 5/19/2006 7:41:39 PM
Author: Capitol Bill
JulieN,

Just a note to say I enjoy reading your posts -- consistently some very thoughtful stuff for someone who claims to not have any industry ties. Of course there are many other ''pro-sumers'' out there whom I enjoy reading as well (too many to list), but I''ve especially enjoyed your posts of late and I''m glad you''re part of this forum.

Cheers!

Bill Scherlag

Since we''re all being sincere and everything... I have to agree with this from a non-expert PofV.... Julie you are great... and when you show flashes of your great sense humor... It''s great to see.