Granite intrusions are found in the parish of Barvas in west Lewis, and another forms the summit plateau of the mountain Roineabhal in Harris. The granite here is anorthosite, and is similar in composition to rocks found in the mountains of the Moon. There are relatively small outcrops of Triassic sandstone at Broad Bay near Stornoway. The Shiant Islands and St Kilda are formed from much later tertiary basalt and basalt and gabbros respectively. The sandstone at Broad Bay was once thought to be Torridonian or Old Red Sandstone.