JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.High-precision trace-element analyses for 208 geological samples representing 25 mesoamerican obsidian sources were obtained using instrumental neutron-activation analysis to measure a total of 28 elements persample. These are the first detailed chemical studies ever published for many of the source areas. Especially intensive analyses were made for six sources in the states of Veracruz and Puebla in Mexico from the region of Pico de Orizaba volcano. In addition, source determinations are provided for 65 artifacts from the Olmec site of San Lorenzo Tenochtitlan, Veracruz. The investigations presented here constitute an important basis for associating obsidian artifacts with specific sources, therety making possible the reconstruction of Prehispanic trade systems.Este informe presenta los resultados de un conjunto de analisis de alta precision realizados por medio de elementos-traza de 208 muestras geologicas procedentes de 25 yacimientos de obsidiana en Mesoamerica. Estos analisis, por medio de activacion neutronica midieron 28 elementos en cada muestra, siendo los primeros estudios quEmicos con este grado de detalle para muchos de los yacimientos. Analisis especialmente intensivos, se hicieron para seis yacimientos de la region del volcan Pico de Orizaba, en los estados de Veracruz y Puebla. Se identificaron tambien los yacimientos correspondientes a 65 artefactos de obsidiana procedentes de excavaciones en el sitio Olmeca de San Lorenzo Tenochtitlan, Veracruz. Nuestras investigaciones constituyen una base importante para la identificacion de los yacimientos especificos de la obsidiana utilizados para los artefactos y mejorar asi nuestro conocimiento acerca de sistemas prehispanicos de comercio. The Prehispanic inhabitants of Mesoamerica extensively mined and traded obsidian from source areas located in two large regions of volcanism (see Figure 1). One region runs east to west from north-central Veracruz through all of central Mexico and continues essentially unbroken through the Bajio and northeIn Michoacan to the Pacific coasts of Jalisco and Nayarit. The other region islocated almost 900 km farther south and runs east to west from the westeIn edges of Honduras to the Pacific coastal regions of Guatemala and E1 Salvador. Both the archaeology and the geology of much ofthe cordillera region along the Pacific coast of Mexico between these two obsidian-containing "volcanic strips" are rather poorly known. It may well be that a number of unknown obsidian sources are located in mountainous areas of Oaxaca, Guerrero, or Chiapas. Paul Schmidt (personal communication 1982) of the Universidad Nacional Autonoma de Mexico, Mexico City, located a source of low-quality perlitic obsidian near...

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33) Hatcher, P. G.; Breger, I. A.; Dennis, L. W.; Maclel, G. E. Prepr. Pap .-Am. Chem. SOC., Div. Fuel Chem., in press. (34) Maciel, G. E.; Szeverenyl, W. M.; Sullivan, M. J., to be submltted for publication. (35) Bloembergen, N. Physlca (Amsterdam) 1949, 15, 386. (38) Gerstein, B. C.; Chow, C.; Pembleton, R. G.; Wllson. R. C. J . Phys. Chem 1077 R I SA5 -. (37) Yokono, T.; Sanada, Y. Friel 1978, 57, 334. (38) Yokono, T.; Miyazawa, K.; Sanada, Y.; Marsh, H. Fuel 1979, 58, 896. (39) Qandy, D. W., Gulf Research and Development Co., private communlcatlon. (40) Retcofsky, H. L.: Stark, J. M.; Friedel, R. A. Anal. Chem. 1968, 40, 1899. (41) Retcofsky, H. L.; Hough, M. R.; Maguire, M. M.; Clarkson. R. B. "Advances in Chemistry Series"; Gorbaty, M. L., Ouchl, K.. Eds.; Amerlcan Chemical Society: Washington, DC, lg8l; No. 192, Chapter 4. (42) Abragam, A. "The Prlnclples of Nuclear Magnetism"; Oxford University Press: London, 1961; p 378. (43) Farrar. T. C.; Becker, E. D. "Pulse and Fourler transform NMR"; Academlc Press: New York, 1971; p 57. (44) Noggle, J. H.; Shirmer, R. E. "The Nuclear Overhauser Effect"; Academlc Press: New York, 1971. (45) Farrar, T. C.; Becker, E. D. "Pulse and Fourier Transform NMR"; Academic Press: New York, 1971. (46) Schaefer, J.; SteJskal, E. 0.; Buchdahl, R. Macromolecules 1975, 8 , 291. (47) VanderHart, D. L.; Earl, W. L.; Garroway, A. N. J . M a p . Reson. 1961, 44, 381. (48) Szeverenyl, N. M.; Sulllvan, M. J.; Maciel, G. E., unpublished work. (49) Dlxon, T. W. Uriano, (3. A.; Gravatt, C. C. Crit. Rev. Anal. Chem. 1977, 6 , Certiflcate of Analysls, Standard Reference Materlal SRM 688 Basak Rock: Office of Standard Reference Materials, National Bureau of Standards, U.S. Department of Commerce, Washington, DC. Certificate of Analysls, Standard Reference Material SRM 278 Obsidlan Rock; Offlce of Standard Reference Materials, Natlonal Bureau of Standards, US. Department of Commerce, Washington, DC. Ondov, J. M.; Zoller, W. H.; Oimez. I.; Aras, N. K.; Gordon, G. E.; Rancltelll, L. A.; Abel, K. H.; Filby, R. H.; Shah, K. R.; Ragaini. R. C. Anal. Chem. 1975, 4 7 , 1102-1109. Germani. M. S.; Gokmen, I.; Sigleo, A. C.; Kowalczyk, G. S.; Olmez, I.; Small, A. M.; Anderson, D. L.; Lepel, E. A.; Gordon, G. E.; Zoller, W. H. Anal. Chem. 1980, 52, 240-245. Certificate of Analysis, Standard Reference Material SRM 1633 Fly Ash; Offlce of Standard Reference Materials,

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A method is reported by which instrumental neutron activation analysis of various heavy metal elements has been applied to the monitoring of nutrient intake of laboratory animals. Some data are presented illustrating reproducibility. The scope of the method may be expanded by utiliza-