Final answer:
A non-metallic fake coin can indeed be heavier than a genuine coin if made of a material with higher density, but most modern counterfeits tend to use materials different from the pure silver or gold of ancient coins.
Step-by-step explanation:
Yes, a non-metallic fake coin can be heavier than a real coin if it is made from a material with a higher density than the metal used in the real coin. For example, ancient coins were often made of pure silver, which has a relatively high density. However, most modern counterfeits are not made of pure silver and might use different materials that can either be lighter or heavier than the original. Counterfeiters have also been known to use heavy metals like tungsten to fake gold coins because tungsten has a density similar to gold. To determine the authenticity of a coin, a common method is to measure its mass in air and then in water to calculate its density. A discrepancy in density could indicate a fake coin.
Historical data on the silver content of coins, like those from Manuel's reign, may show changes in means and variances of coinage, indicating fluctuations in the purity or composition of the metal over time. Such analyses are helpful in authenticating and dating coins.