Mine warfare involved digging under enemy lines to set off large explosive charges intended to collapse their positions. Allied miners used Ammonal for this purpose, an explosive created by mixing ammonium nitrate with TNT, charcoal, and aluminum powder. British and Canadian mines under the Western Front often contained more than 900 kilograms of this explosive packed into 25-pound (11-kilogram) rubberized bags. This portion of an Ammonal bag was found in a chamber at the base of the Grange tunnel system on Vimy Ridge, 76 metres below the surface, by the first caretaker of the memorial site, George Stubbs.
Ammonal Bag Fragment