Obsidian hydration dating range
Obsidian hydration dating range - who is aaron eckhart dating now
Alca is a type of obsidian that is solid and banded black, gray, maroon brown and bottled black maroon brown, that is found in volcanic deposits in the Andes mountains between 3700-5165 meters (12,140-16,945 feet) above sea level.The largest known concentrations of Alca are at the east rim of the Cotahuasi Canyon and in the Pucuncho basin.
The qualities that made obsidian a favorite trade item are its shiny beauty, its easily worked fine texture, and the sharpness of its flaked edges.
See the History of Glass Making, if that's what interests you.
For more rock science on the substance, see the geology entry for obsidian.
The Alca sources are among the most extensive sources of obsidian in South America; only the Laguna de Maule source in Chile and Argentina has comparable exposure.
Three types of Alca, Alca-1, Alca-5 and Alca-7, outcrop on the alluvial fans of the Pucuncho basin.
Journal of Geophysical Research 86 B W and Scalise, J.
In case of measuring the hydration rim using the depth profiling ability of the secondary ion mass spectrometry technique, the sample is mounted on a holder without any preparation or cutting.
The glassy material comes in a range of colors from black to green to bright orange, and it is found everywhere rhyolite-rich volcanic deposits are found.
Most obsidian is a deep rich black, but, for example, pachuca obsidian, from a source in Hidalgo and distributed throughout Mesoamerica during the Aztec period, is a translucent green color with a golden yellow sheen to it.
When this hydrated layer or rind reaches a thickness of about 0.5 microns, it becomes recognizable as a birefringent rim when observed as a thin section under a microscope.
Hydration rims formed on artifacts can vary in width from less than one micron for items from the early historic period to nearly 30 microns for early sites in Africa (Michels et al. Formation of the hydration rim is affected not only by time but also by several other variables.
These cannot be discerned with the naked eye, but they can be identified on the basis of geochemical characteristics, identified through ED-XRF and NAA (Rademaker et al. Stone tool workshops at the sources in the Pucuncho basin have been dated to the Terminal Pleistoceneand stone tools dated to the same 10,000-13,000 year range have been discovered at Quebrada Jaguay on the coast of Peru.