A Great Falls jeweler was sentenced to three years in prison for swapping the diamonds in customers’ jewelery for cheaper stones, a prosecutor said Wednesday.

Robert Mikail, 40, of Ashburn, was convicted of nine counts of grand larceny and grand larceny with intent to sell in October for the scheme which netted nearly $50,000 worth of jewels, a prosecutor said.

Mikail was arrested following a Fairfax County police sting at his Vima Jewelry store last year. An undercover officer took about a dozen pieces of jewelry to the shop to be appraised. After the items were picked up, a second appraiser determined the diamond on a ring had been replaced with a lower quality stone.

When police arrested Mikail, they found the missing diamond on his workbench, according to prosecutors.

The sting was staged after a customer alerted police that Mikail might be stealing diamonds.

Mikail was sentenced Friday. His attorney did not immediately respond to a request for comment.