Photo courtesy of Robert Gray, Center for Big Bend Studies, Sul Ross State University, Alpine, Texas
Arrow points made of various colored agates and chert recovered from a rockshelter site in Brewster County.
Rocks, Rocks and more Rocks:
Their Use by Past Cultures in the Big Bend Region
by Richard W. Walter
T
he Big Bend region is not short on rocks –
they are everywhere! And past inhabitants of
our area took rocks really seriously. Rocks
and minerals were used to make chipped and
ground stone tools, as pigments, items of adorn-
ment, as heating elements to cook food, as construc-
tion material for a variety of features and ceramics,
for ritualism and other uses.
Native groups in the Big Bend cared less whether
a rock was igneous (formed through the cooling and
solidification of magma or lava), sedimentary
(formed through sedimentation) or metamorphic
(formed by the transformation of an existing rock
type through heat and pressure) or that a mineral is
distinctive from a rock. (Minerals have a definite
chemical composition and a characteristic crystalline
structure or may be a compound made up of a num-
ber of chemical elements, while rocks are made up of
one or more minerals.) They just knew that certain
types of stones worked to serve certain functions.
A wide variety of cryptocrystalline materials
were available in the Big Bend for the manufacture
of chipped stone tools. These minerals have a tex-
ture made up of minute crystals and include agate,
chalcedony, chert, hornfels, jasper, silicified wood,
quartzite and siliceous novaculite, basalt, rhyolite,
felsite, mudstone and siltstone, to name a few. The
multi-colored Burro Mesa chert occurs in Big Bend
National Park, while Maravillas chert, a distinctive
black-colored chert, is found near Mara thon. High-
quality, white novaculite is found in the Caballos
Mountains. A variety of beautiful agates are wide-
spread throughout the Big Bend region. Rock
quartz occurs in small amounts within the region
and is the only known crystalline mineral used by
prehistoric groups to make chipped stone tools and
ritualistic paraphernalia as well.
All types of rocks were used to make various
types of ground and pecked stone tools. The most
common types of ground stone tools found in the
Big Bend are metates and manos, because people
relied on them for the processing of various wild
plant materials. Sedimentary rocks used for ground
stone included arenite (or orthoquartzite), sandstone
and sometimes limestone.
Igneous rocks included rhyolite, quartz porphyry
and basalt. Meta morphic rocks included quartzite
and schist. In many cases, natural bedrock expo-
sures and large boulders were modified to create
mortar holes and other grinding surfaces. Other
types of ground stone artifacts include pipes, shaft
straighteners and sinker stones.
Rocks and minerals were also used to create
items of adornment. Kaolinite, a clay mineral, was
by far the most common material in the Big Bend
used to fashion beads and pendants. A pendant
made of chryso p rase, a green-colored variety of
chalcedony, was discovered during an archeological
survey in Big Bend National Park. Even sections of
fossilized crinoids, invertebrate marine animals,
were used for the manufacture of beads.
In most cases, minerals, not rocks, were used for
various colored pigments and include malachite
(green), hematite (red to orange), cinnabar (red),
limonite (yellow), kaolinite (white) and azurite (blue).
Pigments were used for body paint, rock imagery
(pictographs) and decoration artifacts that include
painted pebbles, dart and arrow foreshafts.
Rocks served as heating elements for cooking by
native groups of the Big Bend. Igneous stones such as
rhyolite and basalt were commonly used, along with
some sedimentary rocks such as sandstone and lime-
stone. Heat retention of the type of rock varied, and
certain types of rocks were likely chosen to cook cer-
tain types of foods. Cooking stations range from indi-
vidual hearths, to small roasting features adequate to
cook food for smaller family groups, to larger com-
munal roasting facilities that could produce larger
amounts of storageable foodstuffs such as agave.
Rocks were a major element for the construction
of dwellings, especially those attributable to the
Cielo complex, a Late Prehistoric to Proto historic
(A.D. 1000 - 1700) culture within the Big Bend.
Cobble to boulder-sized rocks were typically stacked
from two to five tiers high around the base of wick-
iups. Other rock features include stone cairns, cysts,
storage platforms, hunting blinds and read-out
localities. Rocks were also used for the construction
of various types of boulder outlines or boulder
mosaics called petroforms.
Rocks were often modified to serve in ritualistic
ceremonies. Some pebbles were painted or incised
and are believed by some researches to have served
in curing and/or fertility rites. Galena (crystalline
lead) was used by the Apache in religion and ritual-
ism. Captain John G. Bourke, an aid to Gen.
George C. Crook, was hired by the U.S. Army to
study the Apache. In his paper “Medicine Men of
the Apaches,” he states:
“At times one may find in the medicine of the
more prominent and influential of the chiefs and
medicine men of the Apache little sacks which,
when opened, are found to contain pounded gale-
na; this they tell me is great medicine. It is used as
face paint and as a powder to be thrown to the sun
or other elements.”
The most common type of artifact found by
archeologists at sites in the Big Bend is made of
stone. Most perishable items have long since
decayed. A great deal of information can be learned
from stone artifacts through a number of special
studies. Rocks and minerals contain specific geo-
chemical fingerprints from a given source area. This
allows archeologists to determine where a certain
type of rock was collected and/or quarried by com-
paring the geochemical make-up of a given artifact
to similar raw material from source areas whose geo-
chemical signature have previously been identified.
This data can give insights on human behavior
regarding trade, interaction and mobility. One of
these analytical techniques is neutron activation
analysis (NAA). This process involves the activation of
gamma radiation to stone artifacts. By measuring the
energy of the radiation, scientists can determine the
presence and concentrations of various elements.
Another type of geochemical analysis is called X-
ray fluorescence. The sample to be analyzed is irra-
diated with primary X-rays and, consequently,
excites electrons from the inner energy levels of the
constituent atoms. When these vacant energy levels
are refilled by outer electrons, fluorescent X-rays are
emitted. The wavelengths of these X-rays are char-
acteristic of the elements excited, thus providing
continued on page 27
Cenizo
Second Quarter 2011
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