Kate wore these oversized pearl and silver earrings to Boujis club in 2007.
Here is the closeup:
The earring appears to be a large silver latticework piece attached to a silver hook. Below this are hung five white pearls. Beneath the three center pearls are attached 3 more white pearls. Beneath the center pearl on the second row is one pearl, forming a deltoid shape.
The closest I could find to a dupe are these from Bella Tiara.