Mining groups BHP Billiton (NYSE: BBL - news ) , Glencore (Xetra: A1JAGV - news ) , Antofagasta (Other OTC: ANFGF - news ) and Rio Tinto (LSE: RIO.L - news ) were down between 2.3 and 4.7 percent.
In the context of the input sentence, determine the relationship between 'Glencore' and 'Mining'.
Options: industry, manufacturer, publisher, employer