There is a curious aside to the story of the pearl in England. In one sense Caesar was proved right. Pearls were found in Britain from before Roman times.
But these, like those found in other fast running streams across northern Europe were not from oysters, but from mussels. These may well have been the ones used in the crowns of early kings.
The Venerable Bede (673-735 AD) lists the things for which Britain was known and writes…“many sorts of shellfish among them mussels in which are often found excellent pearls of all colours; red, purple, violet and green but mostly white”.
The Bishop of Rennes writing in 1070 declared British pearls as the equal of the orient. By the 12th century there was a market in Europe for Scottish pearls, although they did not fetch the same prices as those of the east. By 1355 John II forbade the jewellers from mounting Scottish and oriental pearls together, except for the ecclesiastical ornaments.
In 1521 the Privy Council appointed Pearl Conservators for Aberdeen, Ross and Sutherland to oversee the fishing in July and August, when it was supposedly the best, and ensure the finest examples were secured for the Crown. Paisley in Scotland and Irton in Cumberland were noted pearling places. The Tay, the Teith, the Eran were as well known in Victorian times for pearl fishing as for salmon
Writing in 1908 the jeweller George Frederick Kunz said:
“The summer of 1862 was most famous for pearling owing to the dryness of the season and the low water, and unusually large quantities of pearls were found, the prices ranging ordinarily from 10/- to £2 6s. Queen Victoria is said to have purchased one for 40 guineas…a necklace was purchased for £35 in 1863. The value of the whole catch in Scotland in 1864 was estimated at £12,000 to the fishermen.”
Much more of course to the jewellers and traders.
They may still be found in fast running streams, but it seems they were usually found in older wizened mussels and the agitation in the fast running waters might have started the growth and they needed time to mature. As the mussel industry moved to coastal waters, the English pearl seems to have disappeared.