This paper presents the investigation of fraud and of the theft of metal acquired by a Brazilian company from a Chinese supplier. Zinc ingots were transported by ship from China to the city of Londrina, in Paraná State, Brazil. However, they were substituted at some point during their journey, and replaced with bags containing fine crushed rock. In this case of a classic ‘substitution’ it was possible to use geological methods to investigate the crushed rock. As such, the mineralogical, petrological and isotope analysis showed the replaced rock did not originate from a Brazilian provenance. Therefore, the substitution possibly occurred before the cargo's arrival in Brazil. An inadequate chain of custody of the cargo, during transportation from Asia to Brazil, including the onward journey from Paranaguá to Londrina, is likely to have provided the opportunity for the material exchange to take place. Collaboration between the Brazilian Federal Police and geological experts based in academia enabled the crime to be investigated and solved.