ACCESSIBLE LAB SAMPLES AND RELATED DATABASE OF IGNEOUS ROCKS: MINERALOGY, TEXTURE, AND GEOCHEMISTRY

Geologic collections of rocks and minerals form the backbone of geology programs and courses across the country from the community college to the graduate level as it builds the skills for students to be able to adequately identify, describe, and synthesize a rock’s formation and history based on their mineralogy, texture, and geochemistry. The need for schools to have well-characterized rocks becomes essential for their students’ success. Departments can obtain samples through field collection, donation, or purchasing them from scientific suppliers. The problem with collecting samples directly from the field or from donations is that unless the area has been thoroughly studied in the scientific literature, one is often working without a frame of reference for specific information about microscopic textures and minerals present in the rocks, nor information about the geochemistry. The cost of purchasing samples, that have hand samples and thin sections that are sold as sets, is typically on the order of hundreds to thousands of dollars, depending upon the number of samples purchased. Additionally, even the best sets, such as those sold from Ward’s Scientific, do not come with any information about the geochemistry. This study has begun to develop an inexpensive sample set of igneous rocks that have the mineralogy, texture, and geochemistry that will be easily accessible to any college or university across the country. This is possible because of the universality of “granite” countertops that are sold in kitchen and home improvement stores all over the world. Due to the nature of cutting countertop shapes out of large slabs, there is an abundance of excess material that is either discarded or cut into samples for potential customers. Ten samples were selected to provide a range of plutonic rock types and included: Absolute Crema, Azul Bahia, Baltic Brown, Black Galaxy, Blue Pearl, Crema Springs, Desert Brown, Luna Pearl, Ubatuba, and Volga Blue. These rocks range from gabbronorite to sodalite monzosyenite to monzonite to true granite, with other intermediate compositions as well. The geochemistry of these rocks is also quite diversified even within those classified as “granites” such that a simple selection of counter-tops can provide an excellent base for students to witness the variety of plutonic igneous rocks in class.