Poor polish on cube faces

[pyramid]

I have read that when a diamond is polished on the cube faces the polish is poor, if this is so why would the cutter polish at that angle?

 

[pyramid]

Why would the diamond be cut so the polish is poor? Is it because it is difficult to polish in the direction of a cube face?

 

[RockDoc]

Why is a facet poorly polished? Sometimes it is the nature of a piece of rough that it has to be polished not only orienting the grain properly, but also to adjust the angle of the facet until the facet takes an acceptable polish.

With the stones that are very precisely cut, a stubborn facet can add to the cutting time significantly.

There is also a hard side to the grain and a soft side that also can force the cutter to make adjustments, that if this factor wasn''t present, would sort of go like slicing butter.

This is why diamonds may have varying angles in each facet group. You must grasp the concept that diamond formation of the crystal isn''t uniform.

In science, Mother Nature is the boss, and you can sample thousands of analysis and when you get to the last one after sampling a thousand ( or more ) stones ( or what ever else your testing) that the last one will differ tremendously from the others.
Mother Nature is like this ... I describe it as Mother Nature''s Fickle Finger of Fate, which is usually her middle finger, with a long sharp nail to poke the tester in the eye. All of us in scientific analysis know Mother Nature is very capable of being a
" B I T C H "!

Just when you think you have research that is always conclusive, MN changes all the rules by creating an exception.

Rockdoc

 

[pyramid]

Thank you RockDoc.

 

[Garry H (Cut Nut)]

Pyramid if you do a google search for octahedral diamond crystals then you can imagine that on the oct faces you can polish toward a pointy corner - and this will be very hard, or toward a edge - and this will be softer.
Now if you saw through the center of the stone you have a square face - this is the cube face.
Polishing edge to edge is softer than polishing towards a corner.

(Then imagine you grind one edge - this is the dodecahedra face - and it will have 2 pointy ends - polishing towards the ends is very much harder than polishing across the short side of these facets).

Now with that in mind - a diamond has facets that face in all different directions and there are some facets that need to be polished in each of these 3 softest directions. If you try polish in the wrong direction you can grind a hole or grove in the polishing wheel - you can only polish in a soft direction.

There is plenty of stuff on the net to answer this better and in more detail.
http://www.minsocam.org/MSA/collectors_corner/arc/diamond_hardness.htm

But basically you can see it might be that you might need to polish a diamond near the cube face and finding the softest best cutting direction might be difficult to find.

 

[pyramid]

Thank you Garry, that helps me understand it a lot.