North-Central Section - 39th Annual Meeting (May 19–20, 2005)

Paper No. 5
Presentation Time: 1:20 PM-5:20 PM


PEKAREK, Alfred H., Earth & Atmospheric Sciences, St. Cloud State Univ, St. Cloud, MN 56301,

Rock and mineral “laboratory” exercises were developed for use in large general education auditorium classes in place of the traditional laboratory experience. The exercises give students practice in performing tests on rock and mineral samples to develop and improve rock and mineral identification skills. Each student receives a kit containing 13 common minerals (including the common silicates), 7 igneous rocks (rhyolite, granite, andesite, diorite, basalt, gabbro, peridotite), 3 sedimentary rocks (sandstone, shale, limestone), 5 metamorphic rocks (slate, mica schist, gneiss, marble, quartzite), a small magnifying glass, a streak plate, and a masonry nail. The students are prepared for the take-home exercises by lectures covering the general characteristics, origin, classification, and identification of rocks and minerals. Four exercises have been developed covering minerals and each of the 3 rock groups.

In the minerals exercise, students study hardness, cleavage and fracture, streak, luster, and color. Mineral hardness is compared with the hardness of fingernails and masonry nails. Minerals with 1, 2, and 3 planes of cleavage and concoidal fracture are identified. Streak tests are performed on galena, hematite, and pyrite. Texture, mineral composition, and the relationship between texture and genesis are integral parts of the igneous rock exercise. A cross section containing typical igneous rock bodies has questions to help students focus on the geological context of the rocks they are identifying.

For the sedimentary rock samples students determine mode of origin (organic, chemical, and clastic) and mineral content. Using a small magnifier and a 0.5 mm mechanical pencil, students determine grain size and maturity of the sandstone sample. The weathering products of typical igneous minerals are an integral part of the exercise.

The metamorphic rock exercise includes a study of foliation, mineral content, degree of metamorphism, comparing the strength of quartzite and marble as building materials, textural differences between sandstone and quartzite and between limestone and marble, and identifying the probable parent rocks of quartzite, schist, and marble.