Characterization and Identification of Mineral Unknowns: A Mineralogy Term Project

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ABSTRACT

It is possible in a single term undergraduate mineralogy course to complete a project involving the characterization and identification of mineral unknowns. These identifications are based on physical properties, unit cell parameters or d-spacings determined from powder X-ray diffraction scans, chemical composition determined on an electron microbeam instrument, and optical properties determined with a petrographic microscope. Each phase of the project is timed to compliment the sequence of concepts covered in mineralogy lecture and lab. Such a project serves to (1) illustrate practical applications of methods discussed in lecture; (2) illustrate the connection between mineralogy and topics covered in ancillary courses such as chemistry and physics; (3) pique the interest of some students for pursuing mineralogic and petrologic research projects later in their careers.

INTRODUCTION

Trends in earth science instruction have resulted in reduction in the amount and form of coverage in mineralogy courses and, to a lesser but equally disturbing extent, all of the petrology sub-disciplines (sedimentary, igneous and metamorphic). Single-term courses in "Earth Materials" have widely supplanted the mineralogy-petrology sequence (Brady, 1995), in an effort to make room in the earth science curriculum for courses viewed as more timely or relevant: geophysics, low temperature/environmental geochemistry, hydrogeology, etc. As with many educational trends, this one may return to haunt our discipline in a generation as professional geoscientists are found to lack the background necessary for thorough site and material characterization. Ultimately, regardless of the direction geoscience instructional emphasis swings, minerals, rocks, and surficial materials will be the fundamental materials on and in which we will be performing geophysical, chemical and isotopic analysis, with which the hydrosphere is interacting, and from which we will be fabricating technologically advanced materials. A solid background in mineral science is no less relevant now than it was for previous generations of geoscientists.

A second disappointing trend is the decrease in number of students going on to post-baccalaureate research in mineralogy and petrology. Anecdotal remarks from colleagues in the U.S.A. have made it clear that recruiting students for mineralogy and petrology research has become very competitive. At our institution at least, the vast majority of applications for the graduate program are in hydrogeology. Part of this dearth of students interested in mineralogy and petrology may be related to the experience of students in mineralogy courses. Chances are they weren't shown the practical applications and implications of what they were taught, how what they learned may be relevant to environmental science, or they weren't given hands-on experience with analytical methods in mineralogy and petrology.

A single course in Mineralogy can succeed in providing an adequate background in mineralogy that prepares students for a diverse range of applications in upper division courses (e.g., hand sample and thin section identification for the Ig/Met/Sed sequence; chemical composition and structure for low T geochemistry and hydrogeology). It can serve as a connection with the ancillary sciences that are required by most geology curricula (chemistry, physics, mathematics), often bemoaned by students as not relevant to a geoscience major. The manner in which this is accomplished in our undergraduate Mineralogy course is through the analysis of unknown materials comprised primarily of minerals. As we progress through the semester from physical properties to symmetry to crystal structure to crystal chemistry to optics, students apply the principles of each section to their unknown. They record their observations for each step of the process. By the end of the term, they have completely characterized their sample and prepare a final report compiling all their information. …