Hold the magnet near your gold item. If this magnet gets attracted to the gold item, then other metals are included in it. Gold itself is non-magnetic. Get an unglazed porcelain piece and rub your gold item against the piece. If a black streak is left, then the item is not gold. If you get a yellow streak, then the gold item is pure.
With a magnifying glass examine the gold item closely. The commercially produced jewelry is always marked mentioning the gold purity, like 24 karat or 18 karat or 14 karat. You can take the gold jewelry to any authorized jeweler to determine purity of gold if you don’t want using acid or perform chemical tests.