Optimal cut of stone..

[mochi]

Can someone please educate me on how deep the stone should be to get the optimal beauty of the stone?

For example, if a colored gem is cut as a round brilliant 5.7mm, what would be the best depth of the stone to decrease the possibility of a window? How about for other style of cuts such as emerald cut, cushion, etc?

Also, why is there so many oval cuts on gem stones? Is it because it''s easier to cut it or to keep the high carat weight? What would be one of the most difficult cuts?

So many questions.... thanks!

mimi

 

[PrecisionGem]

There is no one answer to your question. Each gem material has it''s own Refractive index, so there are different angles that would work best for each stone. And then it would depend on the shape of the stone, and also the number of tiers of facets used. What''s more important than depth, is the angle used. What causes a stone to "window" is having facets cut below the critical angle for the stone. This is however so often done most commercially cut stones. Many stones are step cut on the pavilion and what happens is the last tier or two is cut too shallow, less than the critical angle, and this makes the window in the stone. The angles used on the crown will also effect the angles that can be used on the pavilion.

Many stones are cut in an oval because often this gives the best yield for the piece of rough. Typically cutters who spend time with a stone, and carefully plan out the cut will get from 20 to 35% yield from a stone. However cutting houses who cut very quickly will get less, often 10 to 15%. Actually ovals are a cut that takes a bit more time, but when you are paying people pennies an hour, the time doesn''t matter that much. The fasted design to cut is a round, and this is because of the symmetry. You are cutting many facets at the same angle and meeting in the same place. More difficult cuts are the odd shaped stones, things with complex crowns, or checkers boards, as the meet become more critical.

 

[mochi]

Gene, thank you for taking the time to answer my questions. I really appreaciate this.