Mine are cut into discs of wood from a cherry-ballart tree, Exocarpos cupressiformis, which is a wild Australian tree in the Santalaceae, the Sandalwood family. It does bear fruit, though rather strange ones - the actual growing seed is a little hard nut at the very tip of the stem, while the edible part is the swollen stem on which the seed sits, designed to attract birds to eat the whole thing, because the seed needs to pass through a bird gut in order to germinate properly. Many people find the 'fruit' rather bland, but I like it - reminds me of a cashew apple. The early settlers considered the 'cherry with the stone outside' as just one of the many Australian weirds, along with the duck-billed platypus, the echidna, and the seasons being back to front. Anyway, the plant was used in Aboriginal magic and healing, and as a food plant. The wood is good for carving, and I use the sawdust from it in incense.
I used ballart wood because the tree dropped a branch at my feet as I was walking up my front drive on the farm where I used to live at Bridgewater. It was not one I would immediately have thought of using, but since I was walking home from a conversation with the local Ásatru godi, in which he had asked me if I could construct a set of runes for some work with which he had asked me to give a hand, I took it to be a gift, and it worked fine. My original intent had been to cut a branch from one of the old apples or hazels on the property.
If I ever make another set, I'll probably use a branch from the young rowan in my front garden. I need to trim it back soon because it is growing out into the road. And it can certainly be a tree that does bear fruit but is not currently doing so. Cut it in winter, or use a branch dropped in a storm maybe?