It’s a sparkling piece of scandal.

A 300-carat 18th century necklace, whose diamonds may have helped fuel the overthrow of the French monarchy, sold Wednesday for nearly $5 million at an auction in Geneva.

The necklace has been worn at two British coronations and may contain diamonds from the infamous necklace at the heart of a scandal that tainted the reputation of Marie Antoinette, the last queen of France.

It sold for more than twice its estimate, at $4.81 million.

Experts believe that some…