Pure gold is not magnetic, though the magnetic properties of gold jewelry are often a source of confusion for consumers. The interaction a material has with a magnetic field is determined by its atomic structure and the arrangement of its electrons. Gold’s magnetic behavior is subtle and largely imperceptible in everyday life, which explains why a pure gold item will not stick to a common magnet. The noticeable magnetic responses sometimes seen in gold jewelry are entirely due to the presence of other metals mixed with the gold.
The Magnetic Properties of Pure Gold
Pure gold, known scientifically as the element Au, is classified as a diamagnetic material, meaning it is weakly repelled by a magnetic field rather than being attracted to it. This repulsive effect is so minimal that it is virtually undetectable without specialized laboratory equipment. The explanation for this lies in the arrangement of electrons within the gold atom.
Magnetism in metals is largely a result of unpaired electrons, which act like tiny individual magnets that can align themselves with an external magnetic field. Gold’s atomic structure is stable, featuring electrons that are largely paired up, causing their magnetic moments to cancel each other out. This pairing means there is no net magnetic moment to align with a magnet, preventing the strong attraction seen in materials like iron. Therefore, a piece of 24-karat gold, which is pure gold, will exhibit no attraction to a strong magnet.
Why Some Gold Jewelry Responds to Magnets
The gold used in jewelry is rarely pure because 24-karat gold is too soft and malleable for daily wear. To increase its hardness, durability, and alter its color, gold is combined with other metals to create an alloy. These alloying metals are the direct cause of any magnetic response observed in gold jewelry.
The karat rating indicates the proportion of pure gold in the alloy. When ferromagnetic metals like nickel, iron, or cobalt are included in this non-gold portion, they can impart magnetic properties to the entire piece. Ferromagnetic materials are strongly attracted to magnets because they contain unpaired electrons that align in the presence of a magnetic field. White gold, for instance, is often alloyed with nickel, which is a common agent that can cause a slight magnetic reaction. The magnetic pull will be weak compared to an item made entirely of a ferromagnetic material, but it indicates the jewelry is an alloy containing a magnetic metal.
Using Magnetism to Gauge Jewelry Purity
A strong magnet, such as a neodymium magnet, can serve as a quick, non-destructive initial test for gold purity. Since pure gold is non-magnetic, any noticeable attraction or stickiness between the magnet and the jewelry suggests the presence of magnetic alloys like iron or nickel. A piece that shows a strong magnetic response is unlikely to be high-karat gold.
The higher the karat number, the higher the gold content, and the less likely the piece is to contain enough magnetic metal to react with the magnet. Conversely, lower-karat pieces contain a higher percentage of non-gold metals and are more likely to exhibit some magnetic attraction. However, this magnetism test is not definitive for determining authenticity or purity. Many common alloying metals, like copper and silver, are also non-magnetic, meaning that a low-purity item made with these metals would pass the magnet test. Furthermore, small components like the springs inside necklace clasps are often made of steel, a magnetic material, which can cause a false positive even on an otherwise high-purity gold chain.