Study of Portuguese Coins Issued During the Reign of D. João with pXRF Technique and Multivariate Analysis

Portable energy dispersive X-Ray Fluorescence (pXRF) technique was applied for the study of 113 Portuguese coins minted during the reign of D. João I (1385-1433). Multivariate analysis was also employed to obtain more information about the coin set. These coins are part of a collection that belongs to the National History Museum in Rio de Janeiro (MHN). Different Portuguese currencies were studied such as Real Branco, Real de 10 Soldos, and ½ Real Cruzado. The coins were minted with an alloy known as billon, which is made of copper and silver. The reigns of D. João I (1385-1433) and his predecessor, D. Fernando (1367-1383), had intense warlike activity. This activity affected the economy, mainly during the reign of D. João I where the legal content of silver in coins was lower (2.78% weight) in contrast, for instance, with the reign of D. Fernando (8.33% weight). It was verified that some coins have a concentration below the legal value, while an expressive number of coins did not present silver in their composition. A Principal Component Analysis (PCA) was able to separate one monetary value coin regarding the city that it was minted.