He and several SIxer team mates started to wear them after they won 10 games in a row in 1990. Old story.
"In a remarkable start to the 1990 season, Gminski and teammates made a pact that if the Sixers won 10 in a row, they would each get their ears pierced. When the team pulled off 12 in a row, he, Mahorn and the others were sporting diamond earrings to commemorate the feat." (wikipedia)