Formative and Classic Period Obsidian Procurement in Central Mexico: A Compositional Study Using Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry

Abstract

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Role of laser ablation–inductively coupled plasma–mass spectrometry in cultural heritage research: A review

“…Physically obsidian is an homogeneous material characterized by few inclusions and colors ranging from green to gray and black, the latter being by far the most common (see, e.g. [50] for Mesoamerican obsidians).…”

“…The sampling of obsidian tools is accomplished by introducing fragments that are small enough directly in the ablation cell [52][53][54][55][56] or removing small flakes directly from bigger artifacts (typical length minor than 2 mm, see [50,51]). Undoubtedly, the latter marginally compromises the integrity of the object, but shows an important analytical advantage.…”

“…Currently, up to twenty flakes may be mounted and polished on a small epoxy resin disk used as a sample holder [51]. As a consequence, the analysis time is dramatically shortened by eliminating a large number of sample changes [50].…”

“…the concentration of one element, chosen as the internal standard, is determined by means of a different technique (Instrumental Neutron Activation Analysis, INAA or X-Ray Fluorescence, XRF). Silicon is mostly used [50,52,55,57] although sodium [58] and aluminum [55,56] are employed at times, 2. the signals of the analytes (S Ai ) and the internal standard is registered and, after blank subtraction, the first ones are ratioed to the latter (S Ai /S IS ), 3. the analyte to internal standard ratio in the sample is converted into a concentration by comparison with the same ratio in a solid standard material.…”

“…The standards NIST SRM 610 and NIST SRM 612 were originally certified for only eight trace elements, with concentrations around 500 mg/kg and 50 mg/kg in NIST 610 and NIST 612, respectively. These standards were extensively used as calibration standards for obsidian chemical analysis [50,[52][53][54]57,58,60]. Although only a few elements were originally certified by NIST, these reference materials were extensively studied in the past decades and indicative concentrations are available for around 60 trace elements [61].…”