Valued for their lustre and bright appearance, gold and brass are two metals used in manufacturing, jewelry, and other applications around the world. Though they may look similar, gold and brass are two distinctly different metals, and this article will help explain these differences, focusing on how to identify the two.
Gold is a metal known for its bright yellow color and plasticity (its ability to be shaped and formed without fracture). Its chemical symbol is Au, and it is classified as a transition metal. It is pictured above in its purest form. Gold’s applications include jewelry and decoration, investment and economics (gold bars, the “gold standard,” etc.), and electronics. Gold is an expensive metal, classified as one of the precious metals, and has a long tradition of being sought after for its value. Its name is often synonymous with wealth, quality, or prestige – the Golden Rule, the Golden Mean, “good as gold,” “golden years,” etc. Gold is not magnetic, and it does not react to most acids, though it can be dissolved by aqua regia and cyanide, among others. Gold does not tarnish. A carat or karat rating signifies the purity of gold. 24 karat (24K) gold is pure gold, and lower ratings signify that the gold has been alloyed with another metal. Another rating used for gold is known as a fineness rating, which ranges from 0 to 1. 1 is pure gold, and lesser decimal numbers signify gold that is not as pure. Additionally, gold is a very dense metal in its purest forms.
Brass is a metal known for its bright yellow appearance and malleability, and has many applications. These include decoration, fixtures such as doorknobs and locks, ammunition for firearms, musical instruments (e.g. the brass family of instruments or brass strings for certain instruments), and zippers. Brass is an alloyed metal, meaning a metal made from the combination of two other metals. Brass is made from copper and zinc. Pictured abvoe is a brass die to the left, with copper and zinc samples to the right.
|Does not tarnish.||Tarnishes.|
|Does not react with most acids.||Reacts with acids.|
|More dense than brass.||Less dense than gold.|
|More expensive than brass.||Less expensive than gold.|
|Has a purity rating.||Does not have a purity rating.|
|Will mark ceramic gold.||Will not mark ceramic gold.|
Tarnishing is a process of corrosion that occurs on the surface of a metal object. The process is demonstrated in brass bullet casings, pictured below. The second picture shows casings of slightly tarnished brass. This process usually occurs after exposure to air, though it is not just air that can cause tarnishing. Pure gold, because it is so non-reactive, will not tarnish. Alloyed gold can tarnish, but will only tarnish lightly. Brass, however, will tarnish.
While some acids do react with gold, the vast majority of acids will not cause any reaction when coming into contact with gold, whereas brass is reactive with many acids. One way to test for gold is known as the acid test, wherein one puts a drop of nitric acid on the object being tested. If there is no reaction, then the object is pure gold, whereas other reactions usually signify gold plating or other substances like brass.
Another way to check whether an object is brass or gold is to see if there is a karat rating anywhere on the object. Some gold objects will have a karat rating signifying the object’s gold purity. Not all gold objects will have this, however.
Additionally, because gold is so dense, one way to test to see if an object is gold or brass is to weigh the object with the proper equipment and reference materials.
Yet another way to test the object is to scrape it against a ceramic surface. If the object leaves a gold streak, then it is pure gold, whereas a black streak generally signifies another substance.
If the price of the object is available, gold is in all cases far more expensive than brass.