Kate was visiting a nightclub in 2007 when she wore these statement earrings.
Here is the closeup:
Here is the more recent closeup.
They are extremely large earrings. A burnished ball post is the anchor for the pear shaped pendant. The pendant is a concave silver disc with a rim of silver at the borders. It looks like the pendant is gunmetal gray while the ball post is a yellowish gray.I estimated that these are perhaps 3.5 inches long, maybe even longer.
It looks like these are rock crystals, set in a teardrop/small post style. They are possibly set in silver or mixed metals.
Here is a clearer photo of her wearing them.
She may have worn them more recently (December 2016) to a private event.