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Obsidian is a glass, or a super-cooled liquid that is liquid in all its properties except in its ability to flow easily (Cann 1983).

As a glass, its atomic structure, by definition, is entirely disordered.

The formation of silicic glasses (obsidian) is essentially a rare event in nature since a number of limiting factors must occur in order to form a glass.

A brief discussion of rhyolite equilibrium melt reactions will be useful for the understanding of the occurrence of obsidian in the Southwest.

Given the local predilections and vagaries of local CEQA enforcement, we are uncertain if it would have been feasible for Archaeological Research to propose a more extensive program then was undertaken.

Nevertheless, this report identified deficiencies with respect to federal compliance.

Two factors control whether a magma (melt) will form a glass, the rate of cooling and its viscosity, which is determined by its chemical composition. Mount Elden and RS Hill in the San Francisco Volcanic Field, and many of the lesser known domes at Los Vidrios are classic examples of rhyolite dome structures (Nations and Stump 1981).

This incompatibility may be due to the ions being too large for the available ionic sites in the liquid, such as with rubidium (Rb), cesium (Cs), strontium (Sr), and barium (Ba). Picrite 2%), perlitic and/or vitrophyric fabric may form in the glass.Or, it may be due to the ions possessing too high a charge to fit the crystal structure of the solid phase such as the triply charged rare earth elements lanthanum (La), cerium (Ce), and yttrium (Y), the quadruply charged ions of titanium (Ti), and zirconium (Zr), or the quintuply charged ions of phosphorus (P), tantalum (Ta), and niobium (Nb). The resultant perlite or pitchstone is useless for the production of flaked stone tools since the rock exhibits preferred planes of cleavage.As a magma evolves, further melting and crystallization change the nature of the solids, and crystals may form in the liquid which accept the incompatible elements. However, in some lavas, not all the glass will be hydrated and small remnants may occur called marekanites or "Apache Tears", that have not absorbed water (i.e.Qualifications of ASI personnel ate provided in Appendix H.ASI’s report is not meant as a critical review of the technical aspects of the existing report prepared by Archaeological Research, who generously shared all of its project files with ASI and fully cooperated with this investigation.

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