Nine Books on the Nature of Things

Pearls can likewise be made entirely like true pearls in form, so that they cannot readily be distinguished by lustre and appearance. Purify egg white through a sponge as thoroughly as possible. Sprinkle in and mix the finest white talc, mother-of-pearl shell, or Mercury coagulated through Tin and reduced to fine powder. Grind everything very well together on marble into a thick amalgam, then dry it in the sun or behind a warm furnace until it is like cheese or similar. Finally form pearls of any desired size from this mass, attach them to pigs’ bristles and dry them pierced in this way like amber. They are then prepared. If they do not shine enough, anoint their outside with egg white and dry again. Very beautiful pearls result, like true pearls in form but not in virtue.