Gold-filled jewelry is composed of a solid layer of gold bonded with heat and pressure to a base metal such as brass. Some high quality gold-filled pieces have the look, luster, and beauty of 14 karat (58%) gold. By definition, the minimum layer of karat gold in an item
stamped GF must equal at least 1/20 the weight of the total item. 1/20
12kt GF is the most common stamp you will find on gold-filled jewelry.
10kt and 14kt are also common karatages. Gold filled items, even with
daily wear, can last five to 30 years but will eventually wear through.
The gold layer on gold-plated jewelry varies greatly depending on manufacturer, so there is no
single, simple comparison. Gold-filled items are 50 to 100,000 times
thicker than regular gold plating, and 17 to 25,000 times thicker than
heavy gold electroplate