I know this is a silly question

[calamityJJJ]

Hi all. You are all so helpful on this forum. So I know it's okay to ask a dumb question about gem cutting. If you were to cut a stone in half, would it crumble or would you get two equally sized halves?

 

[Lady_Disdain]

As usual, the answer is it depends. Cutting rough is a common activity, of course, but it sometimes go wrong. You can see herea large mahenge spinel being cut, so that it can be fashioned into several stones.

Different materials will behave differently, first of all. If you are trying to cut along a cleavage plane, then odds are it will split cleanly. If you try to do it perpendicularly to the cleavage plane, there is a lot more room for things going wrong.

Inclusions and stress in the crystal may also complicate things. For example, if the diamond blade hits a large inclusion, it can spread and create problems. Tourmaline is famous for stress fractures, where small fractures appear and spread as a stone is cut in a very unpredictable way (most stone cutters have at least one story about the expensive, perfectly clean tourmaline rough that sprouted fractures and ended up a fraction of the estimated size).

I hope one the lapidarists will chime up on this question.

 

[Michael_E]

Assuming the stone is already cut and polished, then yes you'd probably get two equal halves, minus the width of the saw blade. As Lady_Disdain has said, there can always be problems. Saw blades vibrate as does the saw moving through the material and can cause fracturing as the saw exits the stone. There is also significant heat developed when cutting. Both of these things can cause an included stone like emerald to crumble. It can also cause stones with perfect cleavage, like kunzite, to fracture along their cleavage planes, which may or may not be lined up with the saw blade. There's usually not much reason to cut a stone which has already been cut, but it can be an advantage for really shallow stones which would lose a great deal of material in a single re-cut. Turning these into two, smaller stones in a re-cut can save a lot of material and produce a very well matched pair, assuming no color zoning, of course.

 

[chrono]

It depends on the material you are cutting. These varying factors (cleavage, inclusions, internal structure and etc) will all affect the outcome. The best case scenario is that you end up with two pieces of roughly the same shape and size. The worse case scenario is you end up with multiple pieces of varying shapes and sizes. Even if you end up with 2 almost matched pieces of stone, the tone and saturation will always be lesser than that of the original single stone.