Summary: We will talk about the description, systematics, and formation of crystals of some common minerals.  Seven crystal families (lattice systems) will be described along with the shapes, symmetry elements, and some physical properties (e.g. crystal shapes, cleavage, optical properties) that are inherent to those systems with an emphasis on how we can identify these differences in some common minerals.  Visitors will have the opportunity to see models of "ideal" crystals and try their hand at identifying the symmetry elements that define a particular crystal system.  Using petrographic microscopes, visitors will be able to see how different crystal systems can be distinguished using optical techniques (extinction angles, crystal shapes, optical interference figures).  A selection of the best available examples of euhedral (well-formed) crystals will be displayed along with the examples of how they are more commonly found (little to no discernable crystal shapes) and in what rocks they can be found in.  

Biography:  Jeff Thole is the Geology Laboratory Supervisor at Macalester College. He arrived at Macalester in 1996 after doing 5 years of environmental consulting. His work experience also includes spending a year as a geologist for the U.S. Geological Survey in Reston, Virginia. His primary duties include teaching introductory geology labs and maintaining, running, and user instruction for the instrumentation housed in the Macalester Science Division’s Keck Laboratory. Jeff received Master of Science in Geology from Washington State University in 1991 and Bachelor of Science in Geology from the University of Minnesota – Duluth in 1987.