Hyperpyron

The hyperpyron (Greek: νόμισμα ὑπέρπυρον) was a Byzantine coin in use during the late Middle Ages, replacing the solidus as the Byzantine Empire's gold coinage.

The traditional gold currency of the Byzantine Empire had been the solidus or nomisma, whose gold content had remained steady at 24 carats for seven centuries and was consequently highly prized. From the 1030s, however, the coin was increasingly debased, until in the 1080s, following the military disasters and civil wars of the previous decade, its gold content was reduced to almost zero. Consequently, in 1092, Emperor Alexios I Komnenos (r. 1081–1118) undertook a drastic overhaul of the Byzantine coinage system and introduced a new gold coin, the hyperpyron (meaning "super-refined"). This was of the same standard weight (4.45 grams) as the solidus, but of less gold content (20.5 carats instead of 24) due to the recycling of earlier debased coins.

The hyperpyron remained the standard gold coin until gold coins ceased to be minted by the Byzantines in the mid-14th century. It too, however, was subject to gradual debasement: under the Empire of Nicaea (1204–1261), its gold content fell gradually to 18 carats, under Michael VIII Palaiologos (r. 1259–1282) to 15 and under his son and successor Andronikos II Palaiologos (r. 1282–1328) to 12 carats. At the same time, the quality of the coins declined as well, and in the 14th century, their weight was far from uniform. The last hyperpyra, and thus the last Byzantine gold coins, were struck by Emperor John VI Kantakouzenos (r. 1347–1352). The name remained in use thereafter solely as a money of account, divided into 24 keratia.

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