You could put a toothpick through the base and wrap a rubberband around the toothpick and around the rock. They attach fairly quickly.
Just be sure the rubberband isn't to tight. :happyfish
bigarn is on the nose with this one but if its too small for the toothpick method then add some rubble rock in a small cup and put the xenia in the cup this also works...
Super glue gel is IMO the easiest way to do it.
Take a piece of rubble rock, place small puddle of glue on rock. Mash the end of the xenia into the glue and onto the rock.
SiF