This outcrop is mainly maroon to red weathering lapilli and crystal tuff that is typical of the lower Telkwa Formation of the Hazelton Group. The rock here is distinguished by an abundance of maroon and grey feldspar phyric andesite clasts in a feldspathic matrix. These clasts indicate that the rock was deposited near an active volcano in a subaerial environment with oxidation producing a reddish to maroon colour. This is typical of the lower Howson subaerial facies of the Telkwa Formation and is believed to be mainly Sinemurian or older in age.

The lower andesitic pyroclastic member is typically overlain by amygdaloidal basalts. These basalts are often host to copper-silver occurrences which are found as high-grade chalcocite and bornite in intensely epidotized flow top breccias. In the Telkwa Range and on Hudson Bay Mountain well bedded felsic pyroclastic rocks overlie the basalt member; elsewhere this member is absent.

In the Babine Lake area, subaerial pyroclastic rocks of the Telkwa Formation are also found on MacDonald-Sterrett Island (Granisle mine) and in outcrops east of Babine Lake.