1885 668 Unio pearls have often been found in the mounds of the Ohio Valley and the South.
1913 W. J. Dakin 14 The Romans came to Britain for the Unio pearls and there is some evidence to show that they fished the Welsh rivers for them.
1989 25 37/1 The ‘modern’ discovery of Unio pearls in American waters was in Paterson, New Jersey.