From Carob Seeds to Silver: The Story of the Siliqua

Illustrated Specimen Details: Siliqua of the Roman Empire

Example Specimen: Siliqua, 347-355 AD — Later Roman Empire

Historical Context: This silver siliqua was struck during the reign of Constantius II (Flavius Julius Constantius), the son of Constantine the Great, who ruled the Roman Empire from 337 to 361 AD. His era was defined by constant border warfare against the Sasanian Empire and Germanic tribes, alongside severe internal civil wars and religious conflicts.

Design and Inscriptions: The obverse features a characteristic portrait of the emperor wearing a diadem, encircled by the Latin legend D N CONSTANTIVS P F AVG (Dominus Noster Constantius Pius Felix Augustus — "Our Lord Constantius, the Pious and Happy Augustus"). The reverse displays a traditional laurel wreath enclosing the inscription VOTIS XXV MVLTIS XXX. This represents the emperor's vows (vota) to serve the people and the senate for 25 years, with a hopeful extension to 30 years — a milestone he ultimately did not reach. The mint mark ANT at the bottom indicates the coin was produced in Antioch (modern-day Antakya, Turkey), the capital of the Roman province of Syria.

1. ROMAN EMPIRE (4th-7th centuries): siliqua = 1/24 solidus

SILIQUA as a coin name. The siliqua was the principal silver coin of the Late Roman Empire, introduced around 324 AD. Its name derives from the Latin phrase siliqua graeca, referring to the seed of the carob tree. Romans used these remarkably uniform seeds as a standard weight unit (approximately 0.19 grams), a tradition that eventually gave rise to the modern "carat" used for measuring gemstones.

The Evolution of the Roman Siliqua

Introduced during the sweeping monetary reforms of Constantine I the Great (the first Christian emperor on the Roman throne), the siliqua was designed to stabilize the empire's currency system after decades of severe inflation. It gradually replaced the older, heavily debased denarius coin as the standard silver denomination.

Value and Circulation

Within the late Roman gold-silver monetary system, the siliqua was strictly pegged to gold, with an official standard where one siliqua equaled one twenty-fourth of a gold solidus. Because gold was approximately 14 times more valuable than silver at the time, the term "siliqua" came to describe a silver coin worth the equivalent of one carob seed's weight in gold. While its physical silver weight varied across different periods — ranging from 1.3 to 3.4 grams — it was noticeably thinner and broader than the earlier imperial denarii.

Design Legacy and Historical Impact

A distinguishing feature of the siliqua is the highly recognizable, stylized portrait of the emperor or empress wearing a diadem. The reverse designs frequently highlight military standards, Christian symbols, figures of Victory, or commemorative wreaths indicating imperial vows.

The siliqua played a vital role as a commercial currency and military payment method. It circulated extensively throughout the Roman and early Byzantine Empires, and was widely imitated by neighboring Germanic kingdoms, including the Visigoths, Burgundians, and Ostrogoths. A fascinating numismatic phenomenon of late antiquity is the "clipping" of these coins — especially common in Roman Britain — where edges were systematically shaved off to harvest silver while keeping the reduced coin in circulation. Production of the siliqua eventually ceased in the latter half of the 7th century as silver coinage across the Mediterranean sharply declined.