The process involves using a needle to carefully and slightly scratch a part of the gold jewelry; it may be a gold pendant. Gold is then deposited on the needle, and various acids formulated to dissolve certain degrees of gold are dropped onto the needle. The gold purity is determined based on the gold’s reaction to acid. The purest gold resists all but the strongest acids. So, the purer the gold, the stronger the acid required to dissolve it.

This is another distinctive feature of gold. Pure gold in its raw state is very rare and soft such that it isn’t fit for making jewelry. Hence,   mixed with other elements while in its molten state to create alloys with different strengths and colors.  Yellow gold is the most common, containing zinc, copper, and silver. It creates durable gold jewelry, e.g., a gold heart necklace. Closest in color to pure gold, thus a prominent color in jewelry designs.

White gold contains nickel, platinum, or palladium. It was popular in the Art Deco Era. Jewelry made with it, e.g., a white gold necklace, can be plated with rhodium to increase brightness. Rose gold is alloyed with copper and silver like yellow gold but in different proportions. Some contain no silver; the amount of copper presents causes hue variation for different skin tones. A rose gold ring is a perfect example.