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

y bifacial reduction. The only real technological differences between the partially-
bifaced eccentrics and the fully-bifaced eccentrics are ones of symmetry, “quality,” and,
of course, whether the piece was completely reduced using bifacial pressure flaking. All
of the bifacially-worked eccentrics were reduced with bifacial pressure-flaking using a
handheld pressure flaker.
Although some thicker, cylindrical cores were bifacially reduced, the most
common blanks used for bifaced obsidian-eccentrics were exhausted cores with a
lenticular cross section and percussion flakes and blades. A margin was created using an
alternating pressure-technique, whereby flakes are removed in an alternating fashion
from both sides of the core. For unknown reasons, some of the original platform was
retained on the proximal end of the eccentric. For both types of bifaces a bifacial margin
was created around the majority of the piece, but the primary goal of the partially-bifaced
eccentrics was to produce the outline of the symbolic form, rather than to thin the piece.
Fully-bifaced eccentrics, however, indicate that thinning was an important stylistic
element to some knappers. The fully-bifaced eccentrics most resemble the
microcrystalline-quartz eccentrics found at the site. Thus, it is possible that (1) blade-
makers during later times also practiced bifacial reduction of microcrystalline quartzes;
or that (2) exhausted cores were given to experts in biface-reduction techniques usually
associated with microcrystalline-quartz materials. The shift to bifacial reduction of
obsidian at the site suggests that different lithic traditions gained popularity among the
royal family after the demise of Ruler 4, and that political alliances may have given
different groups of knappers access to participate in royal rituals.
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