I think this most likely is Stylidium graminifolium, which is the common trigger plant on Black Mountain. However, to be sure it is not Stylidium armeria, the common one in most of the rest of Canberra, you need a photo/comment showing the narrow leaves (3 mm wide or less) with the obvious midvein on the back of the leaves at the base of the plant. See https://canberra.naturemapr.org/Sightings/1947895