How much is a 10 carat diamond worth?

Anything is worth whatever someone will pay you for it.

Today on Blue Nile, you can purchase a diamond of this weight and spend between US$910,356 and US$1,127,187, depending on the clarity, cut and shade of white diamond you choose.

Best practices dictate that if you own a diamond of this carat weight, that you pay for a certified gemologist to provide you with documentation. This will support your research in establishing a market price for it.