Impatience from the Rev. Edward Daniel Clarke, who probably believed all sorts of unlikely things himself.
The superstition of the inhabitants, not only of Mull, but of the neighbouring islands, is beyond belief. Stones of any singular form.. have each a peculiar characteristic virtue. They are handed with veneration from father to son, and esteemed as a remedy for every species of disease incident to the human or animal race. As there is not in the whole island of Mull a single surgeon or apothecary, it is well for the natives they can have recourse to a mode of relief so universal and so efficacious.
.. It was with much difficulty I could prevail upon these credulous quacks to part with any specimen of their potent charms. I succeeded, however, in purchasing two, during the time I remained in Mull. One of these, a hard and polished stone, evidently appears to have been once used as an axe, or hatchet, and bears a strong resemblance to the specimens of similar instruments brought by circumnavigators from the South Sea islands. The other is of the same nature with the first, with respect to the use for which it was originally fabricated, although it differs in its composition; it was probably once an instrument of war.
By holding the former over the head of any diseased cattle, and pouring water upon it, letting the water at the same time fall on the animal, the beast is said to recover without fail. The latter is a sovereign remedy against barrenness in cows, if it be used in the same way. If either of them be dipped in water, the water cures all pains of the head or teeth, it also removes the rheumatism or sprains in the joints, with a variety of other virtues, too numerous to mention.
Several others which I saw, possessed virtues as various as their forms. Some of these were fossil shells; others like the flint of a gun, called Fairy speds*; and again, others, mere oblong pebbles, which they distinguished by the appellation of 'Cockaroo-hoo-pan', a sovereign antidote for barrenness in the female sex.
* I guess these could have been flint arrowheads. 'Sped' means 'discharged or let go' which sounds like what a fairy might do to an arrow? Also, if anyone's got an axe I'd like to try it on my sciatica please.
From p229 of 'The Life and Remains of the Rev. Edward Daniel Clarke' (professor of mineralogy at Cambridge) by William Otter (1824) - viewable on Google Books.
The RCAHMS record concedes that some of the walling could be Iron Age, though the dun's essentially medieval. The landscape does cry out for something to be on top of these strange features (Dun Ara looks rather like the neighbouring lump in the photo - a flat area raised up suddenly). The dun was covered in bluebells and other flowers when I visited in spring.