Dread Geology

Of the many arcane and occult studies on Arboreus, few unnerve people as thoroughly as geology. In a world of wood, bark, and leaves, the unsettling otherness of stone disturbs to the core. At a cultural memory level, people instinctively know that stone can come from one of two places: the dreaded roots below, or the impossible unknowns of the space beyond the sky.
Most people do not believe in the existence of stone. To them, it is simply on of those imaginary materials in fairy tales or spooky stories to be told around a campfire. But for those who have seen stone, it can be a life-changing experience. Suddenly, the limits of known and unknown are brought into question.
Geologists dive into the uncanny. This borderline-taboo study is split by two schools of research. First are the circle of geologists who study stone brought up from the roots of Arboreus. Stones smuggled up from the shrouded depths are sought after by occultists who wish to tap the arcane essence of What Lies Below. Of course, owning these stones is illegal in many civilized lands, usually for the connection the stones have to the dark underworld rather than the material itself. Thus, whatever knowledge or power is gleaned from these stones tends to only circulate within the secret societies that the occult geologists associate with.
The second circle of geologists are a newer school of study. For the people who do have the misfortune of knowing stone exists, they tend to expect the presence of secret societies and unsavory dealings with smugglers. But what happens when stone appears in the middle of a field high up in the canopy, or in the town square of a village of good, upstanding folks? How could stone get there? This question birthed the second circle of geologists, and their terrible question: what if stone came from beyond the sky? Of course, these geologists were immediately labeled moon-touched at first. How could anything be beyond the sky? But as these mad scientists worked, the mystery only grew. Stones are too heavy to be carried by the wind, too dense to be carried by water, too difficult to work by traditional means before getting caught, if being placed for a prank. So the stones sit, reminders that something may be lurking beyond the known world, until being bought discreetly and carted off by an arcanist who may or may not admit to being a geologist.