The pearls, now part of a necklace that also contains rubies and diamonds, are expected to fetch up to 400,000 pounds (US$815,000; EUR 555,500), according to Christie's auction house.
The jewels were given to Elizabeth Leveson-Gower - the wife of the British ambassador to France and the Countess of Sutherland - and were intended to help Marie Antoinette if she managed to flee the country, Christie's said.
However the former queen never saw the pearls again and was executed by the guillotine in 1793.
The pearls were made into a necklace when Lady Elizabeth's grandson married in 1849. The pearls have remained in the Leveson-Gower family for more than 200 years.
On the second day of the St. Petersburg International Economic Forum, a plenary meeting was held, in which Russian President Vladimir Putin, French President Emmanuel Macron, Japanese Prime Minister Shinzo Abe, Chinese Vice President Wang Qishan and IMF head Christine Lagarde took part