Yes indeed, France had once its river pearls, in the northern part of the country, but the production was very reduced, and apart from local jewelry, they were not much and widely used (compared to Scotland and Germany for instance, where these river pearls were a big affair.).
I think France has always favoured more the salt pearls that came from eastern parts from the world, with which there were many commercial exchanges, from a very long time ago.
Besides, our margaritifera margaritifera from french cold rivers gave rather smallish and roundish pearls, not these long wing shapes that were (and still are ?) found in the Mississipi river for instance.
Empress Jos?phine (wife of Napol?on Ist) tried to breed pearl mussels in the ponds and rivulets in the gardens of her parisian castle La Malmaison ; but it didn't work. She loved pearls and probably expected to gather herself her own necklaces !