The Roman silver coins or dinars were made of silver and were imported from Spain. Thus, it can be inferred that the purity and quantity of silver coins being minted in Rome depended on the amount of silver brought in from Spain. This relation of demand and supply was hit hard once the silver mines of Spain started getting exhausted. This made the import of silver expensive for the Romans. To deal with the situation, the Romans had to stop the production of silver coins. Instead of silver, the Romans used gold for the production of coins. The gold coin or the aureus had a fixed value of 25 denarii.