“The Marie Antoinette pendant is simply irreplaceable,” jeweler Eddie LeVian tellsThe Guardian.

Ancient people even thought pearls were formed when dewdrops fell into clams.

Why, though, are they so pricey?

Marie Antoinette pendant

How natural pearls are formed

Natural pearls are rare, because they don’t really happen organically.

Of the approximately 20,000 different types of bivalves, only a handful can make pearls (viaPearl Guide).

Natural pearls and cultured pearls are different because of the way the irritant is introduced.

Natural pearl on a mollusk

And the bigger and shinier the pearls are, the more expensive and valuable they are sure to be.

How do you tell the difference between a natural pearl and a cultured pearl?

Even trained gemologists can’t tell the difference between the two without the help of equipment like an x-ray.

Mikimoto jewelry

By contrast, freshwater pearls are formed in mussels, and are raised in hatcheries.

Natural and cultured pearls

Freshwater pearls being threaded in China