The Solidus
The Gold Standard of the Roman and Byzantine Empires
The solidus was the legendary gold coin introduced by Emperor Constantine the Great around 310–312 AD in replacement of the debased aureus. Weighing exactly 4.5 grams (1/72 of a Roman pound, or 24 carats/siliquae), it provided absolute monetary stability for over seven centuries.
Known throughout the Mediterranean and Europe as the 'dollar of the Middle Ages' (or bezant in medieval Western sources), the solidus circulated with unwavering prestige from London to Constantinople, Persia, and India.
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| Gold Solidus of Constantine the Great | |
Role in the Byzantine Monetary System
In Byzantium, the solidus (known in Greek as the nomisma) remained the anchor of imperial commerce. Its standard fractions were the semissis (half solidus, 2.25 g) and the tremissis (one-third solidus, 1.5 g).
Under Nikephoros II Phokas in the 10th century, two varieties emerged: the full-weight histamenon and the lighter tetarteron, followed in the 11th century by concave (scyphate) cup-shaped issues before Alexios I Komnenos reformed the gold coinage with the hyperpyron in 1092.
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| Byzantine Gold Solidus | |
Transmission to Western Europe and the Carolingian System
In Western Europe, Germanic successor kingdoms (Visigoths, Ostrogoths, Franks, Lombards) continued to strike tremisses and solidi in the Roman imperial name.
In 781 AD, Charlemagne incorporated the solidus into his classic accounting formula: 1 pound (libra) = 20 solidi (shillings/sous/soldi) = 240 denarii (pence/deniers), establishing the monetary structure of Europe until the 20th century.