Eucharistic Miracle of Siena — Incorrupt Hosts (1730)

On August 14, 1730, thieves broke into the Church of St. Francis in Siena and stole a golden ciborium containing 351 consecrated hosts. Three days later, on August 17, the hosts were found in the alms box of the Basilica of Santa Maria in Provenzano, covered in dust. Despite the theft, exposure to dust, and handling, the hosts appeared intact.

The Ongoing Claim

Unlike most Eucharistic miracles, which are historical one-time events, Siena's case presents an empirically testable, ongoing phenomenon: 223 of the original 351 hosts are still intact nearly 300 years later. Unleavened bread under ordinary conditions typically degrades within months to a few years from microbial activity and moisture.

Scientific Examinations

A 1914 commission examined the hosts and concluded their preservation "reverses the natural laws of conservation of organic matter." A 1922 commission qualified this somewhat, noting that strictly sterile preparation and airtight storage could theoretically allow very long preservation — but concluded that the hosts had not been prepared under such conditions. In 2014, new tests including surface analysis under digital microscopy, ATP (adenosine triphosphate) testing, and microbial culture confirmed continued integrity.

Key Uncertainty

The critical unknown is storage history. The hosts have been in continuous Church custody; no independent continuous monitoring of their storage environment exists. If at any point the reliquary was sealed under low-humidity, oxygen-limited conditions, preservation via desiccation alone might be possible. The 2014 testing, while encouraging, has not been published in a peer-reviewed journal with full methodological detail. This case is the strongest empirical claim of the group reviewed — but "strongest empirical claim" still falls well short of scientific confirmation.