Pearl fishing and selling pearls.
The contributor's father once found a greyish-blue pearl. He gave it to his wife, who wore it by her breast until it regained its solid pink colour. A pearl loses its colour, goes dull, if it is worn by someone you're not close to. They feel the personality of the person wearing them.
Lots of Travellers still  look for pearls in the Rivers Tay, Isla and Esk. Black pearls are the most valuable. A Perth jeweller once paid up to £100 for pearls brought in by Travellers.