This case study presents a multi-technique, fully non-destructive characterization of two Roman coins from the reign of Julian II (361–363 CE): a gold solidus and a silver siliqua. Micro-computed tomography (micro-CT) was used to evaluate internal structure, revealing dense, crack-free material in both coins, with minor inclusions in the gold and slight voiding in the silver. High-resolution optical microscopy and patterned-light optical profilometry identified surface flow lines consistent with struck coinage, rather than casting. Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) further confirmed elemental composition and revealed microscopic platinum-group inclusions (osmium/iridium) in the gold coin—features consistent with ancient refining methods. The silver coin exhibited expected sulfur- and oxygen-rich surface chemistry associated with natural aging and tarnish. Across all techniques, no evidence of modern manufacturing or casting was observed, supporting authenticity and traditional minting processes.
Is This Roman Coin Authentic? Non-Destructive Analysis of a Gold Solidus and Silver Siliqua
Can you tell whether an ancient coin is real without taking a single sample from it? We examined a gold solidus and a silver siliqua from the reign of Roman emperor Julian II (361–363 CE) using micro-CT, optical profilometry and SEM-EDS, all without damaging either coin. The results showed whether each coin was struck or cast and what its internal structure looked like, and they turned up microscopic traces of ancient gold refining.