How much is 5.1 carat diamond color d worth?

Anything is worth whatever someone will pay you for it. Best practices dictate that you take your substantial gemstone to a certified gemologist and pay for a certificate that documents the characteristics of this diamond.

Today on Blue Nile you can purchase such a diamond and pay between US$134,403 and US$594,525, depending on the clarity, cut and exact carat weight that you want.