Filed Under Environment

Buffalo Trail and Montana Street Examples of Slag Boulders

Near the intersection of the Buffalo Trail and Montana Street is rubble of true slag from Butte smelting activity. Oxidized ore veins have been confused with slag because of their similarity in color. Blocks of slag have been used for paving stones and some walls in Butte buildings.


Untitled Note the characteristics of these rocks – along with dark coloration (due to metal oxides), the lack of crystals is clear, and the ropy texture of some of the rocks. These important differences separate slag from natural igneous rocks. The ropy textures formed as the slag cooled after melting in the smelter – much like natural lava flows.


Location: Latitude 46.02067 Longitude -112.53988


Larry Smith, “Buffalo Trail and Montana Street Examples of Slag Boulders,” Story of Butte, accessed April 14, 2024,