Upon Andrew's death in 1301, the throne was claimed by Charles Martel's son, Charles Robert. After a period of instability, he was finally crowned King Charles I in 1310. He implemented considerable economic reforms and defeated the remaining nobility who were in opposition to royal rule, led by Máté Csák III. The kingdom of Hungary reached an age of prosperity and stability under Charles I. The gold mines of the Kingdom were extensively worked and soon Hungary reached a prominent standing in European gold production. The forint was introduced as a currency, replacing the "denars", and soon after Charles's reforms were implemented, the economy of the Kingdom started to prosper again, having fallen into a parlous state following the Mongol invasion.