This impressive mountain, also known as Muckanaght, would be passed in a number of circuits such as the horseshoe walks around the Owenglin or Polladirk Rivers.
As you can see in the picture there is an extensive view of coastline near Letterfrack. On the coastline, just right of centre, is Tully Mountain (356m). Below and to its right in shadow is Diamond Hill.

The summit of this mountain, and the area immediately around it, is composed of schist rather than the quartzite that so much of the rest of the 12 Bens are made of. You can see a single piece of white quartzite on top of the cairn which is otherwise the darker shist. The inset shows one of the pieces of schist in more detail.

This summit attracted the attention of Robert Lloyd Praeger. "The schists ... as on the summit of Muckanaght (2153 feet), and forming as they do a much more hospitable habitat for plant than the barren quartzite, they attract the comparitively few alpine plants of the range - Mountain Meadow-rue, Purple Saxifrage, Mountain Sorrel, Mountain Sawwort, Dwarf Mountain Willow, Holly Fern, and others." Linkback: https://mountainviews.ie/summit/182/comment/700/