The magnetic properties of gold vary significantly depending on its purity. Pure gold behaves distinctly from gold mixed with other metals, which explains why some gold items might respond to a magnet while others do not. This distinction is particularly relevant for 18k gold, which contains a notable percentage of other elements.
Pure Gold’s Magnetic Properties
Pure gold, known as 24-karat gold, is classified as a diamagnetic material. This means that when placed in an external magnetic field, pure gold exhibits a very weak repulsion. A strong magnet will therefore not noticeably attract pure gold.
What Defines 18k Gold
18k gold indicates that 18 parts out of 24, or 75%, of the metal content is pure gold. The remaining 25% consists of other metals, known as alloys. Gold is alloyed to increase its hardness and durability, as pure gold is relatively soft. Alloying metals can also alter the gold’s color, creating variations like white, rose, or green gold. Common non-magnetic alloying metals include copper, silver, and zinc.
How 18k Gold’s Alloys Affect Magnetism
While pure gold is non-magnetic, the 25% of other metals in 18k gold can introduce magnetic properties. If alloying metals include elements like nickel or iron, the 18k gold may exhibit a slight magnetic attraction. For instance, white gold often contains nickel, which is a ferromagnetic material that can make the alloy weakly magnetic. Even small quantities of iron can impart a magnetic response. The degree of magnetism depends on the type and concentration of these alloys, not the gold itself.
Magnet Testing for Gold Authenticity
Using a magnet to test 18k gold provides a preliminary indication of its authenticity, but it is not a definitive test. If an 18k gold item strongly attracts a magnet, it suggests the presence of a high concentration of magnetic base metals, such as iron, which is uncommon for genuine quality gold jewelry. Such a strong attraction might indicate that the item is not authentic gold or contains an unusually high proportion of less valuable magnetic metals. Conversely, if the item shows no attraction to a strong magnet, it does not automatically confirm authenticity, as many fake gold items are made from non-magnetic base metals like brass or copper. Authentic 18k gold should show either no attraction or a very weak one, if any, due to its alloy composition.