In New England Fields and Woods-Rowland E. Robinson

The use of pearls as jewels and their recognition as objects of value date back into the far beyond when the histories of ancient peoples were transcribed upon papyrus. It is very likely that pearls were amongst the earliest gems known to man, and this is not surprising when one considers that the earliest dwellers by the sea probably fed upon the shellfish which produce such objects." This book was written by an Australian zoologist with a view to giving the average reader a summary of the most important facts about pearls, pearl fishing and pearl formation. (from "Pearls")