Research Training Program

Jennifer Maloney
West Virginia University
Morgantown, West Virginia

Mike Wise, Ph.D.
Supervising Scientist
Department of Mineral Sciences

"This has been a wonderful, enlightening experience that has taught me new way to think about problems. I wouldn't have traded this experience for anything in the world."

Cathodoluminescence Study of Feldspars from the Black Mountain Pegmatite, Maine

A pegmatite is a very coarse grained rock that formed from the last part of a magma chamber below the earth's surface. Pegmatites are important because they contain many minerals that are used in industry and they are one of the only places on earth to find gem quality minerals. The importance of studying pegmatites is to understand how such coarse grained rocks formed so that they can be located and mined for their industrial minerals. This research focuses on one specific pegmatite, Black Mountain, located in Maine. Within the pegmatite large crystals of minerals are formed. In the latest-stages of the crystallization of this pegmatite, some fluids were present. These fluids reacted with the minerals that were already formed, causing replacement. These replacement features can be seen only under cathodoluminescence (CL), which is a process were a cathode ray (beam of electrons), similar to the one used in televisions, is reflected onto a thin section of a rock. Under CL, the minerals glow distinct colors depending on their chemical composition. This research looked at the feldspar minerals, mainly the different varieties of the feldspar mineral, albite, that replaced the other minerals in the pegmatite. The goal of the research was to determine how residual fluids affected the pre-existing minerals. Upon examination, it was discovered that there was a decrease in the intensity of the luminescence of the albite when it replaced other minerals. This could be caused by the incorporation of elements that were released during the breakdown of the primary minerals. These elements could not allow luminescence, called quenching, or the elements that caused luminescence, the activators, could react with the released elements and be removed from the mineral. The final possibility is called concentration quenching, which is when too much of the activating elements are incorporated into the mineral and it quenches itself.

This research was supported by a grant from the National Science Foundation Research Experiences for Undergraduates program, Award Number DBI-02435123.

Letter of gratitude