St. Januarius, or San Gennaro, as he’s known in Italian, is the patron saint of Naples, reputed to have died in 325 A.D. He’s celebrated with big festivals in Italy and New York, and you may remember that it was during this festival that Don Corleone (in the younger incarnation played by Robert de Niro in The Godfather: Part 2) assassinated the boss Don Fanucci, with the gunshots masked by the firecrackers in the streets.

But there’s a miracle involving San Gennaro, for a vial of what is reputed to be his blood (about 60 ml) is kept in a glass vessel inside a reliquary at the Naples Cathedral, where three times a year it’s exhibited by the priests. The “miracle” occurring when the solid “blood” liquifies and then becomes solid again. Although the Church won’t officially sanction this as a genuine miracle, they don’t impugn it, either, and won’t permit any tests on the blood except crude spectroscopy through the glass, which has shown some dubious indications of hemoglobin.

Here’s the “blood” liquifying in 2011; at about 3:04 the blood is certified to have liquified, somebody waves a handkerchief, and the crowd goes wild. It’s taken as a good omen (in years in which the stuff hasn’t liqufied, bad things have happened), and assures believers that God is in his Heaven.

Wikipedia describes the ritual:

For most of the time, the ampoules are kept in a bank vault, whose keys are held by a commission of local notables, including the Mayor of Naples; while the bones are kept in a crypt under the main altar of Naples Cathedral. On feast days, all these relics are taken in procession from the cathedral to the Monastery of Santa Chiara, where the archbishop holds the reliquary up and tilts it to show that the contents are solid, and places it on the high altar next to the saint’s other relics. After intense prayers by the faithful, including the so-called “relatives of Saint Januarius” (parenti di San Gennaro), the content of the larger vial typically liquefies. The archbishop then holds up the vial and tilts it again to demonstrate that liquefaction has taken place. The announcement of the liquefaction is greeted with a 21-gun salute at the 13th-century Castel Nuovo. The ampoules remain exposed on the altar for eight days, while the priests move or turn them periodically to show that the contents remain liquid.

The liquefaction sometimes takes place almost immediately, but can take hours or even days. Records kept at the Duomo tell that on rare occasions the contents fail to liquefy, are found already liquefied when the ampoules are taken from the safe, or liquefy outside the usual dates.

There are several naturalistic explanations for this miracle (first described in 1389) that you can read about here and here—explanations hindered by the Church’s refusal to permit invasive sampling (and really, what do they have to gain from that?)  The most viable seems to be that the “blood” is a thixotropic gel, that liquifies when agitated. At CICAP, authors F. di L.Garlaschelli et al. have replicated this phenomenon using materials that would have been available to fakers in the 14th century:

Thixotropy might prove a good hypothesis to explain this “miracle”.  Thixotropy  the property of certain gels to became more fluid, even from solid to liquid, when stirred, vibrated, or otherwise mechanically disturbed, and to resolidify when left to stand. Common examples of such substances are catsup, mayonnaise and some types of paints and toothpastes.

Thus, the very act of handling the reliquary, repeatedly turning it upside down to check its state, might provide the necessary mechanical stress to induce the liquefaction. A successful performance of the rite, therefore, does not need conscious cheating, while not excluding its occurrence, as gentle or sharp movements can certainly control the timing of the liquefaction.

Indeed, over the centuries, unexpected liquefactions have often been observed whilst handling the relic case for repairs.

In support of the thixotropic hypothesis, we made up samples whose properties resembled those of the relic. We used substances that would have also been available in the fourteenth century. After some testing with bentonite clays (producing a thixotropic but unpleasantly mud-like gel), we settled for a reddish-brown FeO(OH) colloidal solution.
This gel is the right shade of brown without the addition of any dye; it becomes perfectly liquid when shaken (See Fig. 1 ) and, just like the relic, can even produce the globo and bubbles on its shiny surface (The real boiling even of a volatile liquid in a closed vessel under such conditions is quite untenable).

All the compounds for this concoction could have been readily available to a Neapolitan artist or alchemist of the 1300s. CaCO3 (from chalk, i.e. limestone, or crushed eggshells) also formed the basis of many white pictorial pigments. K2CO3, available from wood ashes was also well-known, and can be used instead of CaCO3. FeCl3 is available in the mountains around Naples

Indeed, there were several reports in the 14th century of other “liquifying blood miracles.”

However, the blood failed to liquify on the third occasion this year, over a few days in mid-December. An article in Christian Today (CT)describes how Italian Catholics have reacted with fear, for when the blood fails to liquify, as it did in 1939, 1940, 1943, 1973, and 1980 (war and Nazi occupation, cholera epidemic, and earthquake, respectively), bad stuff happens. My view is that the latest failure is connected with Donald Trump. From CT:

Fears of more earthquakes in Italy, cholera and other prophecies of doom circulated on social media after the blood of San Gennaro failed to liquefy.

Gennaro, whose name is often rendered as St Januarius, lived in the third century and is the patron saint of Naples. He is believed to have been a victim of the Roman emperor Diocletian’s Christian persecution.

At his death, it is said, some of his blood was collected by an onlooker and is to this day stored in Naples cathedral in a glass ampoule.

. . . When Pope Francis visited the cathedral in March last year, clergy said they observed the dry blood begin to turn liquid. The blood was said to have “half liquefied”. The three official liquefaction dates are in May, September and December but it does also liquefy for some Popes, although not all, when they visit the cathedral.

This month on the third annual date for the miracle, there were no signs of liquefaction. December 16 is the day Neapolitans remember the eruption of Vesuvius in 1631 and the intervention of San Gennaro to stop the lava before it entered the city.

. . . Fears of more earthquakes in Italy, cholera and other prophecies of doom circulated on social media after the blood of San Gennaro failed to liquefy.

It would be great if scientists could get their hands on this blood, but that’s unlikely. However, the Catholic Church’s ambiguous stand on the issue is canny, for it allows the believers to remain believers without the Vatican having to endorse a sketchy “miracle.”

h/t: Matthew Cobb