windowshopper
Ideal_Rock
- Joined
- Jul 10, 2004
- Messages
- 2,023
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?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.
you are losing me--is that the bottom of the stone?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
oh so what specific facets was he referring toDate: 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....?)
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?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
in english please..........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.
That is a ridiculous generalization.Date: 5/19/2006 2:55:05 PM
Author: codex57
Most immigrants have far better grammar than native born Americans.
garry --i appreciate your input as well!Date: 5/19/2006 5:15:39 PM
Author: Garry H (Cut Nut)
thanks JulieN
very well explained
Date: 5/19/2006 4:53:45 PM
Author: windowshopper
That is a ridiculous generalization.Date: 5/19/2006 2:55:05 PM
Author: codex57
Most immigrants have far better grammar than native born Americans.