i have been offered a lot of 10 untreated rough rubies from Afghanistan with a minimum weight of 5ct per stone.
The stones have a chunky shape. I was wondering how much wastage i have to expect when i get the stones cut and polished.
Depends on how clean they are. You can expect 10 to 35% yield from worse to best case scenario, presuming they are facetable grade in the first place. Do you have pictures of the material? What do you mean by chunky shape?
You are asking for answers regarding the cutting of stones. These are questions for professional lapidaries as anything we provide you are just educated guesses based on our limited knowledge as consumers. You do realize that based on the shapes, inclusions, and size, if the photo is indicative of what you would receive, you will end up with stones smaller than one carat? Not a huge market for stones that size.
I also recall in prior posts you talked about an emerald that you had set in a pendant and had for sale at some trade show. If you are in the trade at all, if you sell for a living, you must declare yourself on this website as trade. Just wanted to clear that up in case it applied to you.
Those stones, if typical, have a great color but the shapes have drawbacks, as always. The surface pitting and cupped fractures on several of them area a concern and the yield that you receive depends upon how particular you are about inclusions and how well the end shapes are allowed to mirror the starting shapes, (it's very hard to get good rounds from long thin pieces, for instance). My advice in this sort of thing is always to not do it unless you have someone with lots of experience available to examine them in person.