Caerulium, also spelled cerulium or cærulium, is a precious metal with a vivid blue color. It is culturally significant but is too soft to make practical tools and is a poor conductor compared to other metals.
Caerulium is only found in a narrow belt surrounding Yih's equator. Surface deposits were historically present in Newman's Dale, though these have been depleted by the time of first contact.
The metal is malleable enough to be cold worked, and its ore can be smelted at relatively low temperatures. It is thought that early shamans accidentally discovered the metal after making fire over deposits of ore.
There are abundant caerulium artifacts both before and after the Theophany. Many Claravian sacred vessels are traditionally made out of or plated with caerulium, such as aspergilla.