How much is a 1 carat marquis cut diamond worth?

Anything you sell is worth whatever someone will pay you for it.

Today, on Blue Nile, you can purchase a one carat marquis cut diamond and pay between US$2,543 and US$17,915, depending on the clarity and colour that you want.

Best practices dictate that you pay a certified gemologist to document the characteristics of your diamond, which will give you a better idea of how to establish a fair market price for it.