9614109 Campbell This is a proposal that aims at studying the mineral pyrite using transmitted near infrared light microscopy. This technique has only recently been applied successfully with other less common opaque ore minerals such as wolframite, enargite, and molybdenite. Preliminary data show that pyrite displays a number of internal features including fluid inclusions, solid inclusions, growth banding, and shear planes. In this study, it will also be assessed if the variable transparency of pyrite is controlled, as in other minerals, by trace element variations. Fluid inclusion studies using this technique may be able to provide information on the conditions of pyrite mineralization. In order to maximize the potential for making microthermometric measurements on pyrite, variations in transparency controlled by chemical impurities, thickness and temperature need to be understood. A better understanding of the IR transparency of pyrite will allow new opportunities to use pyrite in petrological studies to determine its geological origin.