Contrary to what we think, gold is a very flexible material. If a goldsmith would craft jewels out of 24 karat gold, they would very quickly lose their original shape because they would bend or get damaged.
The goldsmith could make these jewels more massive so they would not be able to bend that quickly, but then these jewels would be heavy and expensive. Therefore they add alloys to make gold a stronger material. In Europe 18 karat gold is and was mostly used to craft jewellery. Therefore most of antique jewels from Europe are made with 18 karat gold.
The lovely snakes in the banner picture are for example crafted out of different types of gold. One is crafted in 8K yellow gold, two of these snake rings are crafted in 14K rose gold and the last one is crafted in 18K yellow gold.
