In early Christian tradition, the power of saints’ relics could be transferred from object to object by a simple touch.
The Roman Catholic church classifies the relics of saints into three separate categories. Primary relics are the most important: body parts or fragments of the saints, apostles, or the Big Man himself (for example, the Holy Prepuce), plus a few of the most significant objects associated with Christianity, such as fragments of the cross. Secondary relics are significant objects owned or worn by saints, also common items of veneration. But the third category, tertiary relics, is the funny one: objects that have touched primary (and perhaps secondary) relics. The religiousness in some sense transferred from the important relic to this sort of souvenir relic. The existence of this category of holy relic spawned an entire cottage industry that targeted actual and would-be pilgrims across Europe.
If you went on a pilgrimage, either a big one to the Holy Land, a medium-sized one to one of the key Medieval holy sites (like the Camino de Santiago in northern Spain), or a local pilgrimage to a nearby shrine, you might want to bring back something back – a kind of miraculous souvenir. Most site discouraged chipping off bits of the relics, although this is certainly something that happened, so the idea of tertiary relics gave you a chance to share in the holiness without destroying it.
(Side note: my university lecturer in Romantic literature – now passed away – had a framed sliver of rock in his office. He had chipped it off William Blake’s headstone.)
The image above is one of the Monza ampullae. These tiny jars were made in Palestine around the 6th century CE and carried back to Europe by pilgrims. The jars contained lamp oil taken from the lamps that hung in the various holy sites – their proximity to the points of real veneration giving the oil some kind of tertiary religious property. Other tertiary relics included cloth (wiped on a relic) or clay tokens (baked from the earth near a site). The keepers of relics sometimes charged people for the privilege of creating a new tertiary relic. The Catholic church today forbids the sale of primary or secondary relics, but these tertiary ones are okay to sell – in case you want your own slice of holiness.
[Credit: In Our Time’s episode on medieval pilgrimages.]