The cairn on Sheegouna is to the north-east of Slievenamon and at a height of about 550m meaning from Slievenamon you have to climb down to it.
Jim O'Connor in the link on the folklore calls it "The fairy-fort of the magic cow". He also mentions that there was another cairn on Knockahunna to the north. There is no mention of a passage-grave but this cairn to me seemed to be the more likely of the two to have one.
To the south of the cairn is a rock shelter which may be a megalithic tomb, its not recorded, have a look at the pictures and let me know what you think.
The cairn is smaller than the cairn on Slievenamon so about 2m high by 20m diameter.