Well, vinegar won't actually melt a pearl, but the acids will definitely dissolve one. Pearls are mostly calcium carbonate. Vinegar, which is mostly acetic acid, dissolves calcium carbonate over time. The same dissolution would occur if an egg were placed in a glass of vinegar and left to sit — the egg shell would disintegrate.
More Pearly Facts:
- Mollusks actually create pearls as a form of protection from foreign particles, sand and parasites. Natural pearls, though, are very rare in modern times due to a decline in mollusks as a result of pollution.
- Most pearls are cultured, or grown in mollusk farms with human intervention. Japanese entrepreneur Kokichi Mikimoto invented the process in 1888 when he started his pearl oyster farm. The company he started still sells pearl all over the world today.
- Don't bother looking for a pearl in a plate of oysters-on-the-half shell. Edible oysters don't produce nacre, a protein and mineral secretion required for pearl formation.