These instructions about how to clean gold jewelry also apply to gold-filled jewelry. By U.S. law, gold-filled means that at least 1/20th of the weight of the piece is a layer of gold (often 14k gold) that has been bonded by extreme heat and pressure to base metal (usually brass). Through that process, the outer gold layer becomes joined with the inner core of base metal (the “filled” in gold-filled) and the result is jewelry that has the appearance of gold, but is stronger and costs much less.
It's important to clean gold-filled jewelry gently to avoid scratching the outer layer of gold. Better yet is to store the pieces so carefully they rarely need cleaning and never need any polishing other than a gentle rub with a soft cloth to remove fingerprints.