The Organization of Chipped-Stone Economies at Piedras Negras ...

they all have unique architectural schemes and site layout. While reason for these
differences is unknown at this time, the obsidian variability adds to the characterization
of these household groups as functionally and historically distinct locations.
First, the cutting-edge-to-mass ratios are more variable than other closely situated
residential groups at the site. Cutting-edge-to-mass (CE:M) ratios have been interpreted
as an efficiency rating for blade production because knappers of greater skill should be
able to produce thinner and longer blades (Mitchum 1989). It may also mark different
core reduction strategies. In the near periphery, the CE:M ratio for RS29 is only 4.84,
which is the lowest in the site, and RS6 is 6.17, which is akin to the rest of the producing
residential groups (Table 7.2). This variation may indicate that (1) more than one
producer supplied blades to the near-periphery; (2) that they were importing ready-made
blades; or (3) a variety of blade reduction techniques were used in this area. Of the RS
residential groups that feature obsidian production evidence, only RS6 yielded a full
range of production debitage. The general lack of first-series blades at these sites may
indicate that they received cores that were partially reduced by pressure. The
technological differences between obsidian samples indicate that the near-periphery
groups used obsidian in different ways than those in the site center. In sum, the
irregularity of the obsidian sample shows that blade production was not common in this
area, and that exchange and production of obsidian goods here was unique. It is possible
that more households in this area were involved in blade-production during Chacalhaaz
times, but they do not fit the pattern set out in this study, nor do they resemble other
producing households from the city center. It is possible that itinerant blade-makers were
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