The question of whether real gold is magnetic is a common query, especially for those attempting to test the authenticity of jewelry or bullion. The simple answer is that pure gold is not attracted to a standard household magnet. Understanding gold’s interaction with a magnetic field requires looking beyond simple attraction to the underlying physics of how different metals behave at the atomic level. This interaction is a defining characteristic that helps distinguish gold from many other common metals.
The Magnetic Identity of Pure Gold
Pure gold, specifically 24-karat gold, is definitively non-magnetic in the sense most people understand the term. It will not stick to a permanent magnet, no matter how strong the magnet is in a typical home setting. This property results from gold being classified as a diamagnetic material.
Diamagnetism means that when gold is placed within an external magnetic field, it develops a very weak magnetic field that opposes the external one. This slight opposition causes a minute repulsive force, pushing the gold away from the magnet. However, this repulsion is so weak that it is completely imperceptible without highly sensitive laboratory equipment.
The internal reason for this behavior lies in the structure of the gold atoms themselves. All of gold’s electrons are paired up, meaning there are no unpaired electrons to align their spins in the presence of a magnetic field. Because there are no unpaired electrons, gold cannot be attracted to a magnet.
Understanding the Types of Magnetism
Materials are categorized into three primary groups based on how they respond to a magnetic field, with the differences rooted in their electron configuration.
The strongest interaction is ferromagnetism, exhibited by metals such as iron, nickel, and cobalt. These materials possess unpaired electrons whose magnetic moments spontaneously align within domains. This leads to a powerful attraction to a magnet that persists even after the external field is removed.
A weaker form of attraction is paramagnetism, seen in metals like aluminum and platinum. Paramagnetic materials contain unpaired electrons that temporarily align with an external magnetic field, causing a slight, weak attraction. This induced magnetic field disappears instantly once the external magnet is taken away.
Gold falls into the third category, diamagnetism, which is characterized by weak repulsion rather than attraction. In diamagnetic substances, all electrons are paired. The application of an external magnetic field causes a slight shift in the motion of these electrons, which creates a tiny, opposing magnetic field.
Practical Implications for Gold Jewelry
While pure gold is not attracted to a magnet, the vast majority of gold used in jewelry is not pure, but an alloy. Jewelry is typically made from 10-karat, 14-karat, or 18-karat gold, meaning it is mixed with other metals to increase hardness and durability. These alloying metals are the reason why a gold item might react to a magnet.
If a piece of gold jewelry shows a noticeable attraction to a magnet, it is due to the presence of a ferromagnetic metal in the alloy. Common alloying metals include non-magnetic ones like copper or silver. However, highly magnetic metals such as nickel, iron, or cobalt are also introduced to the mixture. For instance, nickel is frequently used in white gold alloys to achieve its pale color and increase strength.
The magnetic test is a useful initial screening tool, but it is not a definitive purity test. A strong attraction indicates either a very high concentration of magnetic alloys or that the item is merely gold-plated over a magnetic base metal like steel. Conversely, a lack of attraction does not guarantee purity. The gold may be alloyed with other non-magnetic metals like copper, which would still result in a non-magnetic response, requiring further testing for authentication.