According to the Gazetteer for Scotland these islands include Luing, Seil, Shuna, Torsay, Easdale, Belnahua and Fladda. W. H. Murray in The Companion Guide to the West Highlands of Scotland goes so far as to say: Seil and Luing, Shuna, Torsa, Belnahua and many others are collectively known as the Slate Islands. Torsa is a tidal island, joined to Luing at low tide. From a geological perspective Shuna has no workable slate, although limestone was once worked there. The neighbouring islands to the west, Lunga and Eilean Dubh Mòr, are constituted of quartzite, Scarba conglomerate and other rocks that lack a commercial value.