The value of your jewelry will depend on how much gold it contains. This might sound odd when talking about ‘gold jewelry’, but gold is almost always mixed with another metal to reduce its cost.
The system for classifying the purity of gold uses a unit known as the karat, which was defined by the ancient Romans and Greeks. 24 is the maximum number of karats, so absolutely pure gold is said to be 24-karat gold. The system works using fractions, so you can say that 18-karat gold is 75% gold, 25% other metals; similarly, 12-karat gold is composed half of gold and half of other metals.
The process of mixing metals is known as alloying, and takes place with the metals in the molten state at high temperatures. Once they’re mixed in this way, it takes a similar process to reseparate them. This is why it’s important to see the markings on gold, as they indicate that specimen’s purity.
So in answer to the question of how much your jewelry is worth: There’s no easy way of knowing. This is why it’s important that you take it to a reputable jeweler, who will examine it and give you a proper valuation. Be extremely wary of sending your gold for valuation in the free envelopes that often come through the door. Only use them if they offer full insurance, and be sure to document and photograph all items you send.
Valuation is easier if you have evidence of the gold’s purity or history, and if the hallmarks are still intact.