7:30 PM: Presentation
The twin point or center, the twin axis, and the twin plane all add additional symmetry to crystals. What are the optical properties that manifest themselves by twinning, what optical property look-alikes are not due to twinning, and how does this information help the researcher using polarized light microscopy? Types, mechanisms and causes of twinning, twin laws, polymorphism, polytypism, lattice defects and aperiodic (quasi-) crystals will be presented along with a brief history of crystallography. The ultimate question: What is a Crystal?

Bio Sketch
Bill C. Mikuska received his BS and MS in chemistry from the Illinois Institute of Technology with emphasis in physical chemistry and chemical physics. Research studies included gas-surface interactions by molecular beams and X-ray induced defects in alkali halide crystals. A 30 year teaching career at Triton College followed where he engaged students to use polarized light microscopy in independent study projects. He was president of the State Microscopical Society of Illinois for 9.5 years and has received the Emile Chamot award. Bill is also a fellow of the Royal Microscopical Society. He taught classes in polarized light microscopy to high school students, high school and middle school teachers, and engineers at Fermi National Accelerator Laboratory and at the Argonne National Laboratory. Most recently he became a member of the Rowfant Club, a bibliophilic society founded in Cleveland in 1892. His interests range from classical music (organ performance and practice), Venetian and French glass, antique bronzes, art, meteoritics, mineralogy, and botany.

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