The gold solidus was a gold Roman Empire coin that was later issued under the Byzantine Empire. The gold solidus was first struck in the early 4th century and became the cornerstone of one of the longest-standing and most influential monetary systems in history. The solidus endured for more than seven centuries as a symbol of economic stability and imperial authority.
Historical Significance and Context
The gold solidus was introduced by Emperor Constantine the Great in AD 312 to replace the gold aureus and restore financial stability to an empire plagued by inflation. Constantine’s reform standardized the solidus at 72 coins per Roman pound (approximately 326.6 grams), giving each coin a weight of about 4.5 grams.
To ensure a stable gold supply, Constantine drew on war booty, confiscations from pagan temples, and newly imposed taxes. The coin’s high intrinsic value was equivalent to about 275,000 debased billon denarii, which restored trust in imperial currency and facilitated large-scale commerce, tax collection, and military payments.
Composition, Minting, and Design
Composition
The solidus was composed of high purity gold around .958 fine. Its weight remained a consistent 4.5 grams, reinforcing its role as a unit of currency and weight (1⁄72 of a Roman pound). This made it the preferred medium for numerous domestic transactions, international trade, and tax obligations.
Minting and Production
The primary mint for the solidus was Constantinople, though important branch mints operated in Antioch, Ravenna, Thessalonica, Carthage, and Syracuse. Some locations, such as Carthage, produced globular solidi, which were smaller and thicker. Other locations, like Syracuse, issued solidi with lower weight and gold content.
Design
The coin’s design evolved over time, reflecting political shifts and religious transformations.
Roman Solidus (4th–6th Century)
Early solidi issued under Constantine the Great and his successors featured traditional Roman depictions of Emperors portraits in profile, clad in laurel wreaths or armor on the obverse. The reverse featured depictions of Roman gods and virtues like Victory. Later, Christian symbols like the cross began to appear, as under Theodosius II and Anastasius I.
4th–5th Century
Constantine the Great (AD 306–337)
- Obverse: Constantine with laurel wreath or crown.
- Reverse: Roman gods or military themes.
- Introduced the gold solidus, which remained relatively unchanged in weight and purity for centuries.
Theodosius II (AD 408–450)
- Obverse: Bust of Emperor with armor and spear. Reverse: Victory, holding a scepter and cross.
- Gold solidus often depicted him with a spear over his shoulder, a conventional portraiture style at the time.
Anastasius I (AD 491–518)
- Obverse: Three-quarter bust in military dress.
- Reverse: Victory in profile, holding a long cross. Reforms included the introduction of the bronze follis, which helped stabilize the economy.
6th Century
Justin I (AD 518–527)
- Obverse: Front-facing bust.
- Reverse: Angel replaces Victory.
- Coins issued under Justin I marked a transition from the Roman to the Byzantine style, with an angel replacing Victory.
Byzantine Solidus (6th–11th Century)
As the Byzantine Empire took shape, the solidus design shifted to reflect Eastern Christian iconography. As a Byzantine coin, frontal busts of reigning emperors became standard, often accompanied by regalia like the globus cruciger. Some coins, like those of Heraclius, included multiple figures to emphasize dynastic succession.
6th Century
Justinian I (AD 527–565)
- Obverse: Emperor with globus cruciger.
- Reverse: An angel holding a cross and globus cruciger.
- Best known for legal reforms and the construction of the Hagia Sophia, the principal church of the Byzantine Empire. Coins under Justinian II emphasized Christian motifs like images of Jesus Christ and angels.
Justin II & Tiberius II (AD 565–582)
- Obverse: Featured stylized busts.
- Reverse: Personification of Constantinople or cross on steps.
- The cross on the reverse symbolized a gigantic cross erected at the Cavalry by Theodosius II.
7th Century
Phocas (AD 602–610)
- Obverse: Bearded emperor with cross.
- Reverse: Standing angel.
- Coins under Phocas departed from the historical standard of showing Emperors clean-shaven.
Heraclius (AD 610–641)
- Obverse: Emperor with his son. Inscription:
- Reverse: Cross atop three steps.
- Heraclius’ desire to strengthen his dynasty was reflected by the inclusion of his sons alongside him.
10th–11th Century
Constantine IX (AD 1042–1055)
- Obverse: Bust of Christ
- Reverse: Emperor Constantine holding a scepter and globus cruciger.
Michael IV (AD 1034–1041)
- Obverse: Portrait bust of Christ.
- Reverse: Bust of Michael IV holding labarum and globus cruciger.
Primary Uses of the Solidus
The solidus served as the empire’s gold coin for major payments, including:
- Paying soldiers and government officials
- Collecting taxes
- Conducting international diplomacy and tribute
- Supporting large-scale commercial exchange
Purchasing Power
In the Fourth Century
- 200 modii of wheat (roughly 1,724 liters)
- Several sheep or a cow
- Wages for several weeks of skilled labor
- A small plot of land or a year’s rent on a larger property
In the Seventh Century
- 100 modii of wheat (about 862 liters)
- Several sheep or a cow
- One year’s rent on land
- Construction labor, e.g., 30 solidi to build a 100-foot well
This underscores the solidus’s purchasing power, even as broader economic conditions shifted.
By the 11th century, the solidus suffered systematic debasement. Alexios I Komnenos eliminated the debased solidus in 1092, replacing it with the hyperpyron, a new standard at 85% gold. Its impact can be seen and felt in numerous respects, including language. The word “soldier” derives from solidus, reflecting its centrality in paying troops. Though the coin ceased minting in the 11th century, its impact shaped medieval and early modern currency systems.
From Constantine’s reforms to its 11th-century retirement, the solidus served as a model of monetary resilience. Its legacy endures in the coins, currencies, and languages it helped shape, securing its place as one of the most iconic coins in world history. Through nearly three-fourths of a millennium, the gold solidus was the gold standard in the Roman and Byzantine worlds.
