Sam Swanson

Petrology of Granitic Rocks

My interest in granitic rocks comes from a summer internship with the USGS mapping in the Sierra Nevada batholith. I mapped and did a petrologic study of a granitic pluton in the western Sierra Nevada for my Masters thesis at U. C. Davis. More recently I have worked on the pegmatites. Two studies (Veal, M. S., 2004; Susina Senior Thesis, 2010) involved students. A study of samples of spodumene pegmatites from the Kings Mountain District of North Carolina involved over 20 undergraduate students from my Earth Materials class and produced one senior thesis (Saenger, 2012)

Crystal Growth and Development of Igneous Textures

I was part of the Luth-Tuttle -Jahns experimental petrology group during my Ph. D. studies at Stanford University. I continued my experimental studies at Stanford for several summers after my graduation in 1974. The main focus of my work was the growth of feldspar and quartz from undercooled granitic melts. These studies documented the fundamental difference between textural development in plutonic rocks and volcanic rocks by quantifying the crystallization kinetics. The quantification of the undercooling required to produce cellular quartz led to the recognition of the importance of undercooling even in plutonic systems.

More recently, results of these experimental studies were applied to textures in the pegmatites at Spruce Pine and to the cellular tourmaline in the granite at Stone Mountain, Georgia (Longfellow, M. S., 2009). Ultramafic Rocks of the Southern Appalachian Mountains

Ultramafic Rocks of the Southern Appalachian Mountains

Ultramafic rocks in the southern Appalachian Mountains have provided resources to people for thousands of years. Ancient Americans carved the soft soapstone into bowls in pre-ceramic times. More recently these deposits yielded a variety of industrial minerals including olivine, asbestos, vermiculite, corundum, and chromite.

Together with colleagues and my students (Cole, Senior Thesis, 2012, Duhamel, M. S., 2013) we have documented the polymetamorphic history of these rocks and attempted to look beyond the metamorphic overprint to determine the petrotectonic significance of these rocks.

Petrology of Archaeological Materials

I grew up on a ranch in central California. One of our fields contained a Native American, Pomo camp site. After each tilling of the field I would find lots of obsidian fragments and an occasional arrowhead. Grind stones used to make acorn meal were common in a creek at the site. This was my first experience with stony archaeological materials. The geoarchaeology program at UGA provided a way to professionally expand on my boyhood interests in geoarchaeology. We use this obsidian in my graduate class on the Petrology of Stony Archaeological Materials as a evolving class project.

Current research projects focus on the application of traditional petrologic tools (petrographic microscope; electron microprobe; X-ray diffraction; major, and isotope geochemistry) to characterize archaeological materials. My graduate students work on a variety of ‘stony” archaeological materials. Graduates worked with Roman-age slags from Carthage, Tunisia (Nikki Lyle, M.S., 2002), 3000 year old glass from Iran (Stapleton, Ph.D. 2003; Demosthenes, M. S., 2013), and Spanish ceramics (Cranfill, M.S. 2006) from colonial Maryland. More “stony” projects include Georgia soapstone (Radko, M. S., 2011; Duhamel, M.S., 2013), muscovite from Etowah Mounds (Bonomo, M. S., 2011), turquoise from New Mexico (Cranfill, M. S., 2011), and marble from Greece and Turkey (Babcock, M. S., 2012). A current student, Joanna Wilford, is just starting a project on the mineralogy of matrix cement in Angkor Wat (Cambodia) sandstones.