Runes are historically carved from wood, not stone, for divination.
Here is a part from 'Germania' by Tacitus concerning his witnes of Rune use-
Auguries and Method of Divination. Augury and divination by lot no people practise more diligently. The use of
the lots is simple. A little bough is lopped off a fruit-bearing tree, and cut into small pieces; these are distinguished
by certain marks, and thrown carelessly and at random over a white garment. In public questions the priest of the
particular state, in private the father of the family, invokes the gods, and, with his eyes toward heaven, takes up
each piece three times, and finds in them a meaning according to the mark previously impressed on them. If they
prove unfavourable, there is no further consultation that day about the matter; if they sanction it, the confirmation
of augury is still required. For they are also familiar with the practice of consulting the notes and flight of birds. It is
peculiar to this people to seek omens and monitions from horses. Kept at the public expense, in these same
woods and groves, are white horses, pure from the taint of earthly labour; these are yoked to a sacred car, and
accompanied by the priest and the king, or chief of the tribe, who note their neighings and snortings. No species of
augury is more trusted, not only by the people and by the nobility, but also by the priests, who regard themselves
as the ministers of the gods, and the horses as acquainted with their will.
Southern Cruisers Riding Club