The Ugly History Of Beautiful Things: Pearls
There are stories of pearls falling out of women’s mouths when they utter sweet words, and pearls appearing from the spray of sea foam as a goddess is born. To create an iridescent pearl, the organism must be able to secrete nacre, a calcium carbonate substance that hardens over time. Pearls were all the rage in ancient Egypt and Rome, and many of the wealthiest women in society wore them to demonstrate their wealth and status.
Source: longreads.com