Copper Compositional Data
I have often been asked to publish the trace element composition data that I have developed for copper source samples and prehistoric copper artifacts from North America. The data are published as an appendix in my recent book, but I have made them available here for researchers interested in further exploring the sources of copper and the social interactions that moved it throughout a large portion of the continent.
These data were developed through the use of the facilities of the Institute for Institute for Integrated Research on Materials, Environment, and Society (IIRMES) at California State University Long Beach. I am indebted to Hector Neff of CSULB and IIRMES for his assistance and guidance in the use of the IIRMES facilities and equipment.
Copper samples were analyzed using Laser Ablation Inductively Coupled Plasma Mass Spectrometry, or LA-ICP-MS. LA-ICPMS was performed on the copper samples using a New Wave Research UP-213 Laser Ablation system coupled with a GBC OptiMass 8000 ICP time of flight mass spectrometer. Three standards were used for data calibration, including SRM 1107 Naval Brass, SRM 500 Unalloyed Copper, and SRM 1110 Red Brass. Laser ablation of samples was accomplished using 300 to 550 mJoules with at least one ablation pass to clean the sample prior to starting the spectrometry. Ablation passes to remove potential contaminants and oxidation were conducted with the laser set with a 100 μm beam, while the laser was reduced to a 50 μm beam for the spectrometry passes to further limit the potential for contamination. Many of the artifact samples exhibited oxidation of varying thickness, and a video magnification system allowed for real-time observation of the ablation process, providing a clear view of the point at which the oxidized layers were ablated from the sample and clean copper was visible. Spectrometry was only attempted after it appeared that the oxidized layers had been largely or completely removed.
The resulting data records concentration of thirty five elements in parts per million (ppm). Due to the near purity of native copper, the element Cu dominates each sample, often comprising over 99.9 percent of the sample. These ppm data will therefore need to be normalized prior to any statistical analysis. Several methods present themselves, but I use the following Power Transformation to normalize the data: X(λ) = X1/5 – 1/(1/5)
These data are subject to copyright, and while intended for the use of researchers their use must always be cited as follows:
Hill, Mark A.
2012 Appendix VII Copper Trace Element Data in The Benefit of the Gift: Exchange, Ritual, and Emergent Regional Systems in the Late Archaic Western Great Lakes, pp 375-398. International Monographs in Prehistory. Ann Arbor, Michigan
These data were developed through the use of the facilities of the Institute for Institute for Integrated Research on Materials, Environment, and Society (IIRMES) at California State University Long Beach. I am indebted to Hector Neff of CSULB and IIRMES for his assistance and guidance in the use of the IIRMES facilities and equipment.
Copper samples were analyzed using Laser Ablation Inductively Coupled Plasma Mass Spectrometry, or LA-ICP-MS. LA-ICPMS was performed on the copper samples using a New Wave Research UP-213 Laser Ablation system coupled with a GBC OptiMass 8000 ICP time of flight mass spectrometer. Three standards were used for data calibration, including SRM 1107 Naval Brass, SRM 500 Unalloyed Copper, and SRM 1110 Red Brass. Laser ablation of samples was accomplished using 300 to 550 mJoules with at least one ablation pass to clean the sample prior to starting the spectrometry. Ablation passes to remove potential contaminants and oxidation were conducted with the laser set with a 100 μm beam, while the laser was reduced to a 50 μm beam for the spectrometry passes to further limit the potential for contamination. Many of the artifact samples exhibited oxidation of varying thickness, and a video magnification system allowed for real-time observation of the ablation process, providing a clear view of the point at which the oxidized layers were ablated from the sample and clean copper was visible. Spectrometry was only attempted after it appeared that the oxidized layers had been largely or completely removed.
The resulting data records concentration of thirty five elements in parts per million (ppm). Due to the near purity of native copper, the element Cu dominates each sample, often comprising over 99.9 percent of the sample. These ppm data will therefore need to be normalized prior to any statistical analysis. Several methods present themselves, but I use the following Power Transformation to normalize the data: X(λ) = X1/5 – 1/(1/5)
These data are subject to copyright, and while intended for the use of researchers their use must always be cited as follows:
Hill, Mark A.
2012 Appendix VII Copper Trace Element Data in The Benefit of the Gift: Exchange, Ritual, and Emergent Regional Systems in the Late Archaic Western Great Lakes, pp 375-398. International Monographs in Prehistory. Ann Arbor, Michigan