The older part of the tower is constructed in limestone ashlar, with greenstone rubble used in the 20th-century re-building; it also contains some red brick.
A north-northwest-trending crustal segment transects from Kaminak Lake (central Hearne Domain) in the south to Yathkyed Lake (northern Hearne Domain) in the northwest, consisting of Archaen supracrustal belts that preserve mostly Archean mafic to felsic volcanic rocks (greenschist-grade supracrustal and granitoids), metamorphic cooling of hornblende and Proterozoic biotite.