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Dimension of rough


#1

By using specific gravity of a rough stone and knowing the weigh of stone in carat, How do we calculate the dimension of the rough in mm? and how do we guess the dimension of the cut ? It has been in the articles by I could not see , how it has been calculated? please help


#2

I think the calculation you might be referring to is how to estimate the carat weight of a finished gemstone based on its cut, dimensions, and specific gravity. Those formulas are found in this article. (I’ve added this link to the gemstone physical properties article, where Donald Clark mentions this procedure but doesn’t elaborate). Also, we have a chart of standard gem sizes where you could estimate the carat weight of a diamond needed to fit standard gem dimensions and cuts.

I don’t think you can use these formulas to calculate the dimensions of gem rough. (Rough pieces can come in many shapes anyway). At best, you could figure out the carat weight of a piece of rough you would need to cut it to fit a standard size gem setting. That is, you would know you have to have a piece of rough that weighs more than “x” so you could cut it to fit that size.

These formulas are most useful for estimating a finished gem’s carat weight when you can’t remove it from a setting. Although I think you could convert the formulas to solve for a specific dimension “x” if you already know the carat weight and the other dimensions, you’re better off just measuring the gem. I think the settings pose less of a challenge to measuring a gem’s dimensions than to weighing the gem.

I hope this helps.


#3

That’s correct, there are no such formulas for estimating yield from rough given SG & mm dimension. There are just too many variables with rough. The closest thing to what you’re asking for is the diamond modeling software used by diamond cutters. As I understand it, the software both maps rough and suggests possible size/shape/orientation options for the cutter. Rumor is someone is working on a similar thing for colored stones. But for the moment, it’s the experienced eye of the gemcutter who can give you the best estimate of what a rough will yield.


#4

It took long time for me to read majority of the articles on this website and also about what you mentioned above as I was very busy with my job.
I appreciate your comment
Mazyar


#5

I wish there was a software too for color rough stones too but as you mentioned there is not any
I think it is just the practice and someone else mentioned that I have to have a depth to width ratio of 60% to not run into a lower cut angle (lower than critical angle) but if it happen for the rough then it could be a custom cut under circumstances. I am trying to see what I can find in lower price like a cheap quarts in smaller size and odd shape to practice this theory and see what is the result.
I just bought the machine and for that reason I wrote to you late.
Anyway, thanking you for your comment.
Maz