Optical Microscopy Systems and Video Display in Under- graduate Petrography Laboratories

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Modern laboratory investigations in petrography, the study of the mineralogy and textures of rocks, go far beyond traditional methods of transmitted light microscopy. We are requesting an optical microscopy system to bring new equipment and techniques into our undergraduate curriculum. The equipment includes a polarizing microscope with both transmitted and reflected light systems to display all three types of images. Cathode luminescence is sensitive to specific trace elements in minerals; it highlights subtle textures produced by sequential crystal growth that are not visible in transmitted light, and permits rapid identification of certain minerals. Reflected light allows identification of opaque minerals and study of their intergrowths. With the video system we can dramatically increase efficiency and clarity in instruction of petrographic methods: we will all be looking at the same feature at the same time. The alternative is painstaking interaction with each student, taking turns viewing an image in the scope. The students will use the instruments in a series of new classroom exercises and in undergraduate research. The video display also allows instructive demonstrations in introductory classes to show the importance of synthesizing several types of information.