This rare Italian marble can cost over $420 per square foot. Here's why.

Michelangelo's famous "David" sculpture was carved out of marble. The iconic material has been used for centuries by artists and designers alike. And calacatta is one of the world's most expensive types of marble. It’s more than double the price of carrara marble, yet mined in the same mountains. But the key to calacatta's price is its rarity.