Telling the difference between a gold coin and a bronze coin could mean the difference between a coin worth a few dollars and one worth hundreds. But with a few simple tools, one can easily tell the difference.
Take a look at the color of the coin. Bronze coins are typically a deep-brown color, or at least a variant of brown. Bronze is a loose term that conveys a wide range of copper alloys, which means that copper is combined with tin, aluminum or nickel. But typically, Bronze is 60 percent copper and 40 percent tin or nickel. Gold has a distinctive color, like honey yellow, and may also have copper spots depending on the alloy. While a bronze coin can look like gold, a gold coin rarely looks bronze.
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Weigh the coin. Place the coin on a scale that measures to the hundredths, or to two decimal places.
Learn the standard weight for the coin. Most coins produced in the modern era have standard weight tolerances. This means a modern gold coin will weigh its intended weight Bronze is a less dense metal than gold, so if you have two coins of the same size, one being bronze and the other gold, the gold coin will weigh more because it is more dense. For U.S. coins, almost any guidebook on the subject will have coin weights.
Compare the weight of the coin with the standard weight. Does the coin match the weight in the guidebook for the given coin? If so, it likely is the metal that it claims to be.
If still unsure, take the specific gravity of the coin. The specific gravity measures the relative density of a metal. To measure specific gravity, one weighs the coin in water. The complexities of specific gravity measurements go beyond this particular article, but an accurate reading will make the composition of your coin clear.
Generally, gold does not corrode. If the coin has corrosion on it, it is likely not gold.
Avoid destructive testing with acids as it may seriously damage the coin and affect its value.