What is gold-filled: 14k gold-filled material basically means that the core metal (usually brass) is encapsulated in a thick layer of 14 karat gold. As such, the value of gold-filled findings fluctuates with the rate of gold. The layer of gold is 100 times thicker than that of gold-plated findings, ensuring that the piece is tarnish resistant. If cared for well, gold-filled jewelry can last a lifetime. Gold-filled jewellery typically requires light surface cleaning with untreated cloth.