X-Ray Florescence – A Nondestructive Method to Analyze Curated Artifacts
In May 2011, Cave Archaeology Investigation and Research Network (C.A.I.R.N.) received a grant from the Missouri Humanities Council (MHC) for operating costs of the pXRF (portable X-Ray Florescence) in Missouri. The equipment retails for $25,000, and simply insuring it for 6 months costs over $600, so the MHC grant was a welcome help. The pXRF is an instrument designed for non-destructive collection of elemental composition samples in caves and other field environments. The opportunity to use X-Ray Florescence Project allowed C.A.I.R.N. to document archaeological features and conduct analyses on curated artifacts using nondestructive methods.
C.A.I.R.N. used the pXRF to sample six collections in Missouri and Indiana
Washington University, St. Louis
The first test using the pXRF by C.A.I.R.N. was at the Washington University in St. Louis, Missouri in May 2011. Dr. John Kelly had requested the C.A.I.R.N. team use the pXRF on basalt samples collected from a site near Cahokia Mounds and from a region near Lake Superior in Canada. Results were provided to Dr. Kelly as pXRF scans were made of the basalt samples. The analysis could tell Dr. Kelly if the basalts came from a local source within Missouri or from glacial erratics deposited long ago in the region. Data examination is ongoing.
Right: Susie Jansen (CAIRN) taking a pxrf reading from a basalt sample at Washington University in Saint Louis.
Center for Archaeological Research, Missouri State University, Springfield
In June 2011, the pXRF was used to scan five collections housed at the Center for Archaeological Research. The first collection was utilitarian ceramic vessel fragments from Totogal, Veracruz, Mexico. The majority of these sherds are varieties of “Coarse Brown” vessels. This pilot XRF study of Coarse Brown sherds from Totogal will begin to examine intraware patterns regarding the use of non-kaolin clays to determine if Coarse Brown ceramics are good candidates for further compositional study.
The second test collection at the Center for Archaeological Research involved prehistoric ceramics from the La Reconnaissance site in Lopinot, Trinidad. Examples of these different paste recipes, as well as source clays from the Lopinot River Valley are currently being subjected to analysis at the Missouri State University Research Reactor. This XRF study will provide complimentary data to those collected. The goal of each analysis is to determine whether different clay sources are represented in the different paste recipes used as well as to obtain preliminary information regarding local distribution/consumption networks.
The third test collection at the Center for Archaeological Research involved artifacts collected from the historic Delaware Town (A.D. 1822 to 1831) along the James River, Missouri. The historic artifacts were recovered by Missouri State University field schools between 1999 and 2005. C.A.I.R.N. researchers used the pXRF on artifacts from the Delware Town collection, some silver and brass items. The research question was whether these artifacts were high quality silver or German trade silver, which contained little to no actual silver. The data gathered from the pXRF concluded that the silver artifacts were in fact high quality silver. Neal Lopinot concluded that the silver might have been obtained earlier, prior to the Delaware arrival in Springfield, Missouri.
The fourth test collection at the Center for Archaeological Research involved artifacts from the 1861 Civil War battle site near the confluence of the James River and Wilson Creek. On August 9, 1861, Colonel Franz Sigel received orders from General Lyon to move down the Yoakum Mill Road toward the southwest. Captains Eugene Carr and Charles E. Farrand, their cavalry troops, and artillery now numbering 1,118 men and six pieces of artillery joined Sigel. Sigel and his men moved into battle, which was fought and won by the Confederate forces. In 2007, Missouri State University archaeological field school performed a formal investigation where the battle was believed to be fought. The investigation was performed by metal detection survey, systematic shovel testing, and formal excavation of nine test units to locate and identify cultural materials. A number of civil war materials, particularly munitions, were found at the site. C.A.I.R.N. researchers scanned the collected civil war munitions with the pXRF. The Center for Archaeological Research is currently analyzing the data collected.
The fifth collection tested at the Center for Archaeological Research consisted of one hundred different chert pieces collected from the Ozarks, with primary focus on look-alike chert types. Some of the collected cherts are Ordovician in age and some were Mississippian in age. Jack Ray hopes with this research that trace elements using the pXRF can differentiate some of the look-alike cherts. A lot of overlap and variability could prove this task difficult. Jack Ray is currently analyzing this research.
Glenn Black Laboratory of Archaeology, Indiana University, Bloomington
In September of 2011, C.A.I.R.N traveled to Indiana University to sample a fluorite collection, from the Angel Mounds site in Indiana with Dr. Tim Schilling. This included a well-known and priceless artifact known as “Little Green Man.” The Green Man is a fluorite statue found in a mound cap deposit that radiocarbon dates to after 1400 A.D. The goal is to use the pXRF elemental analysis data to help identify the composition of the fluorite from the Angel Mounds site to assist in determining regional procurement sourcing. Different trace element inclusions in some of the fluorite sampled may be helpful in tracing sources as well. Fluorite is found in the Ohio River Valley and the goal is to gain a better understanding of where the material came from, the trade and local geographic interaction spheres.
Left: “Little Green Man” photographed at Indiana University
Field Use of the pXRF
The pXRF was also used in a field setting to examine archaeological features in situ. In May 2011 on the Mark Twain National Forest, the C.A.I.R.N. research team sampled disturbed soils along the cave floors of a cave in Phelps County, MO. Mike Tennant and Natalia Kolk-Tennant of C.A.I.R.N. created a one meter square grid which included all areas in the cave where cultural material was excavated previously (in the early 20th century) and artifacts noted on the May 2011 trip. C.A.I.R.N. researchers are currently examining the elemental analysis samples and comparing results with previous early 20th century excavation maps. The disturbed floors of a cave in Pulaski County and a second cave in Phelps County were also examined with the pXRF as a comparison. Once analysis is complete, the data will be submitted in a report to the Mark Twain National Forest.
The second field project using the pXRF was in a cave in Dade County, Mo. In 1985, a sinkhole entrance collapsed in a Missouri farm field exposing a prehistoric time capsule. The cave housed human footprints in mud, torch marks and rock art. In June 2011, the rock art was scanned in a nondestructive method using the pXRF. The samples were collected from three separate petroglyphs in the cave. The pXRF would enable elemental composition examination of each petroglyph image without damage or removal of the image. Samples were also taken of blank cave walls for quality control comparison.
In addition, two other caves known to contain petroglyphs/rock art were sampled for comparison using the pXRF. In June 2011, the C.A.I.R.N. research team sampled historic writing on the walls of a cave in Christian County, Missouri. This cave in Christian County contains a prehistoric lithic scatter and historic 19th to 20th century etchings on the cave walls.
In September 2011, the C.A.I.R.N. researched team used the pXRF at a rock art cave in St. Genevieve County, Missouri. Prehistoric petroglyphs along the cave surfaces were scanned carefully with the pXRF. C.A.I.R.N. hopes the analysis will provide evidence of trace elements of pigment or tool use unnatural to the cave. An overall examination of the data from the three caves (Ste Genevieve County cave/Dade County cave/Christian County cave) will be combined in a paper/report and presented at the XRF Conference in August 2012.
The equipment grant for the pXRF loan from Olympus and the monetary assistance from the Missouri Humanities Council allowed C.A.I.R.N. a rare opportunity to assist numerous archaeologists in their research and for a chance to gain a better understanding of the elemental changes present in the cave setting that bear hallmarks of human interaction. Data analysis in many cases has just begun and the data collected will be part of an ongoing canon for further comparative research.
Above: Using the pXRF to collect rock art data in Lon Odell Memorial Cave, southwest Missouri
Above: Craig Williams (white helmet) Mike Tennant (red helmet) of C.A.I.R.N. collecting rock art data
Right: Uktena or Underwater Spirit petroglyph