223
OC8SIDIAN SIIDIES IN 1984
Fred Stross
Twenty years have elapsed since the publication of the first papers showing
that the sources of obsidian glass could be determined by physico-chenical
methods. Since that time, the quality of the analytical determinations has
i   ved, leading to real confidence in the source assignments; provenience
detezminations have been correlated with dating procedures, thus complementing
arhaeological infonration, and criteria have been suggested that allow those
interested to assess the reliability of the deterninations. Data banks repre-
seating detailed compositions of obsidian sources are being established in many
region and cost effective procedures are beimng developed which enable the user
to reduce the cost of determinning provenience. Attenpts to use computer tech-
niques to improve interpretation of results, or further to reduce the cost,
continue to be made. Finally, other physical measurements have been developed
which have contributed to the infonration desired, such as the measurement
of obsidian hdyration to determine the time at which the obsidian was last wrked.
My specific conts on the papers in this volume will be restricted primarily
to those dealing with obsidian source analysis, since obsidian hydration analysis
is covered in detail in the following paper by Meighan.
Hughes' paper fittingly sets the tone by enphasizing that producing high
quality data is mrre important than using sophisticated statistical, computerized
methods for their intepretation. The statistics needed to make valid proven-
ience assignmnts on the basis of high quality data are relatively simple; if
the data are not sufficiently discriminating to make such assignments, this fact
is normally quite obvious without the use of canplex techniques. I think it was
very worthwhile for Hues to have gone to the trouble of pointing out in detail
how treacherous it can be for the non-expert in statistics to use advanced methods
and how, in the few amrbiguous cases, misratch by computer is at least as likely
as mitch on the basis of simpler calculations.
Nelson's article reflects careful work, and his data generally compare very
well with data obtained by other workers on some of the same sources. They
provide a useful addition to the data bank on Great Basin obsidian already avail-
able in the literature.  However, given the reservations expressed by Nelson on
page 29 of his paper, I am unsure why the author used discriminant analysis to
distinguish between sources.  In my estimation, computers are useful in obsidian
analysis for cataloging data and for performing routine analytical calculating
and evaluating functions, but in the interpretive techniques that have become so
fashionable in this type of study, the pitfalls for many practitioners are far
more significant than the benefits they are likely to gain, as noted previously
by Hughes.
Hampel's paper is much to the point, concisely and competently discussing
some problem  in x-ray fluorescence analysis that are most commonly ignored i
obsidian analytical studies.
Bettinger, Delacorte and Jackson explore the utility of visual sourcing.
They make the point that in a limited geographic area, some obsidian sources can