GEOL 211 Final, Spring 1998

* Pe icay CSIVERSIT hIBRAR Y er re teed mae | _ a The American University of Beirut Final Examination Crystallography/Mineralogy (211) June 23, 1998 Department of Geology Time: 2 hours Dr. A.M. Abdel-Rahman Exam rules apply Part I Answer all questions in Part I (MARKS ) (20) 1. (a) Describe the so-called "Biopyriboles", and give a mineralogical example. (b) How do pyroxenoids differ from pyroxenes; name a pyroxenoid mineral, and give its composition. (c) Zeolites have been used for a number of applications; Discuss one of these applications, with emphasis on the role of substitution. (d) Give the general formula of a dioctahedral mica, and of a trioctahedral mica, and give the coordination number of the various structural sites in the formulae. (e) Given below is a diagrammatic sketch of the structure of chlorite. Describe this structure in detail. Tale layer Brucite-like layer Concisely describe the structure of the three polymorphs of Al,Sio,, with special reference to Al- coordination polyhedra and structural sites. Comment on the importance of these minerals for petrologists (use diagrams along with text to illustrate your answer). Give the exact chemical formula for each of the following minerals. Aragonite Leucite Microcline : Ilmenite Enstatite muscovite Anthophyllite Almandine Cristobalite ! j}) Fayalite To which crystal! system does each of these point groups belong: mm2, 422, 23, 2/m, 432, 3/m 3/m 3/m, 6/m, 2 (a) List all the crystal systems, and give a mineral example for each system. (b) What is the point group that each of the following five stereographic projections represent; \a—pos/ aN