Sourcing archaeological artifacts has proven extremely useful in discerning prehistoric trading patterns and cultural contacts. This study widens the scale of many past sourcing projects by considering an entire museum’s collections rather than an individual object type or site. Advancements in the technology of geophysical sourcing, such as non-destructive reflectance spectroscopy, have made access to many previously restricted artifacts possible. By analyzing much of the pipestone collection housed by the Smithsonian’s National Museum of Natural History using reflectance spectroscopy, existing notions of prehistoric trade on the plains may be detected and supported.

Pipestone Sourcing

The term ‘pipestone’ refers to any clay argillite used by Native Americans to carve pipes or other ceremonial objects. Catlinite, a red pipestone from southwestern Minnesota, is by definition only found at its source outcrop in Pipestone County, Minnesota, yet its popularity often causes archaeologists to erroneously label the majority of red pipestones as such. Only by sourcing artifacts can the true place of origin be identified. Reflectance spectroscopy allows for the identification of a stone’s mineralogical components by measuring the amount of infrared and visible light energy that an object absorbs or reflects. Several prehistoric pipestone quarries are known to exist, and each of these known quarries possesses a unique mineralogical composition.

Reflectance Spectroscopy

Reflectance spectroscopy is the study of how matter absorbs or reflects energy. A spectrometer is the instrument used to create and measure this interaction by first emitting the necessary energy onto the surface of an object, and then by detecting and measuring the amount of that energy reflected back. The spectrometer will produce a unique spectrum for each unique mineralogy; therefore, each pipestone quarry (possessing a unique mineralogy) will possess a unique spectrum. The spectra produced by the analysis of pipestone artifacts can then be compared to the spectra of known pipestone quarries in order to discern their source location (geological provenance).

ASD Terraspec

The spectrometer employed in this study is the ASD Terraspec, manufactured by Analytical Spectral Devices. The Terraspec employs visible, near infrared, and short-wave infrared energy to analyze objects. The instrument is non-destructive, portable, and extremely sensitive for detecting mineralogical properties.

Collections

In total, 213 objects were analyzed for this study. The majority of these objects (188) were from the archaeological collections of the NMNH, while the remaining 25 objects were from the collections of the NMAI. Seven different types of pipestone were found within the sample set, including Minnesota catlinite, Baraboo pipestone from Wisconsin, Kansas pipestone, Ohio pipestone, and three types of undocumented pipestone of unknown provenance. Nearly three-quarters of the sample set was in fact made of catlinite. The distribution of catlinite through space was then mapped.

Trading Inferences

The next step in the project involved the movement of pipestone through time. This was done by plotting the objects of known time periods and tracing the movement of source material from quarry (geological provenance) to archaeological provenience. The resultant maps demonstrate the movement of pipestone through time and space, and support present notions of pipestone use, especially the use and trade of catlinite, which is believed to have been traded in Woodland times, and then again, more fervently, during late prehistoric and historic times after a period of hiatus.

Conclusions

Analysis of museum collections provides the researcher an opportunity to view broad patterns through time and space. This study also illustrates the beneficial collaboration of geologists and archaeologists to achieve a more holistic understanding of past cultures. A complete inventory and evaluation of pipestone artifacts, especially catlinite, must be conducted if the cultural, social, and economic importance of these materials is to be understood, and how those variables have changed through time.

Pipestone Quarry on the Couteau des Praries by George Catlin (1836-1837)