Fall Out Boy rocker Pete Wentz got political at the NME Awards in Los Angeles on Wednesday night (23Apr08) by scribbling 'Coltan Is A Conflict Diamond' on his T-shirt.
The bass player was protesting the mining of coltan diamonds in Africa.
The gem, which is used in the manufacture of mobile phones, has become a massive commodity that some say is now more valuable than gold.
It's mining has led to warring rebel groups in the Democratic Republic of Congo exploiting coltan to help finance war - an issue raised in Leonardo DiCaprio's hit film Blood Diamond.
Wentz told reporters, "People have got to be careful what they buy."
The rocker went on to state that the engagement ring he bought his new fiancee Ashlee Simpson was not made with conflict diamonds: "I trust the jeweller. He's a reputable person."