archaeology Archaeology or archeology is the study of human activity through the recovery and analysis of material culture. The archaeological record consists of Artifact (archaeology), artifacts, architecture, biofact (archaeology), biofacts or ecofacts, ...

, a prismatic blade is a long, narrow, specialized stone flake tool with a sharp edge, like a small razor blade. Prismatic blades are flaked from stone cores through

pressure flaking In archaeology, in particular of the Stone Age, lithic reduction is the process of fashioning stones or rocks from their natural state into tools or weapons by removing some parts. It has been intensely studied and many archaeological industrie ...

or direct percussion. This process results in a very standardized finished tool and waste assemblage. The most famous and most prevalent prismatic blade material is

obsidian Obsidian ( ) is a naturally occurring volcanic glass formed when lava extrusive rock, extruded from a volcano cools rapidly with minimal crystal growth. It is an igneous rock. Produced from felsic lava, obsidian is rich in the lighter element ...

, as obsidian use was widespread in Mesoamerica, though

chert Chert () is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a prec ...

flint Flint, occasionally flintstone, is a sedimentary cryptocrystalline form of the mineral quartz, categorized as the variety of chert that occurs in chalk or marly limestone. Historically, flint was widely used to make stone tools and start ...

, and

chalcedony Chalcedony ( or ) is a cryptocrystalline form of silica, composed of very fine intergrowths of quartz and moganite. These are both silica minerals, but they differ in that quartz has a trigonal crystal structure, while moganite is monoclinic ...

blades are not uncommon. The term is generally restricted to

Mesoamerica Mesoamerica is a historical region and cultural area that begins in the southern part of North America and extends to the Pacific coast of Central America, thus comprising the lands of central and southern Mexico, all of Belize, Guatemala, El S ...

n archaeology, although some examples are found in the

Old World The "Old World" () is a term for Afro-Eurasia coined by Europeans after 1493, when they became aware of the existence of the Americas. It is used to contrast the continents of Africa, Europe, and Asia in the Eastern Hemisphere, previously ...

, for example in a Minoan grave in

Crete Crete ( ; , Modern Greek, Modern: , Ancient Greek, Ancient: ) is the largest and most populous of the Greek islands, the List of islands by area, 88th largest island in the world and the List of islands in the Mediterranean#By area, fifth la ...

. Prismatic blades were used for cutting and scraping, and have been reshaped into other tool types, such as projectile points and awls.

Morphology

Prismatic blades are often

trapezoid In geometry, a trapezoid () in North American English, or trapezium () in British English, is a quadrilateral that has at least one pair of parallel sides. The parallel sides are called the ''bases'' of the trapezoid. The other two sides are ...

al in cross section, but very close in appearance to an

isosceles trapezoid In Euclidean geometry, an isosceles trapezoid is a convex quadrilateral with a line of symmetry bisecting one pair of opposite sides. It is a special case of a trapezoid. Alternatively, it can be defined as a trapezoid in which both legs and bo ...

. Triangular blades (in cross-section) are also common. The ventral surface of the prismatic blade is very smooth, sometimes bearing slight rippling reflecting the direction of applied force and a very small bulb of applied force (indicative of pressure reduction). Flake scars are absent on the ventral surface of these blades, though eraillure flakes are sometimes present on the bulb. The dorsal surface, on the other hand, exhibits scar ridges running parallel to the long axis of the blade. These facets are created by the previous removal of blades from the core. The proximal end contains the blade's striking platform and its bulb of applied force, while the distal end will consist of a snap break, a feather termination, or a stepped termination.

Production

Obsidian Obsidian ( ) is a naturally occurring volcanic glass formed when lava extrusive rock, extruded from a volcano cools rapidly with minimal crystal growth. It is an igneous rock. Produced from felsic lava, obsidian is rich in the lighter element ...

prismatic blade production was ubiquitous in Mesoamerica, and these tools can be found at a large majority of Mesoamerican

archaeological site An archaeological site is a place (or group of physical sites) in which evidence of past activity is preserved (either prehistoric or recorded history, historic or contemporary), and which has been, or may be, investigated using the discipline ...

s from the Preclassic period on until the arrival of the Spanish in the early 16th century. Ethnohistoric sources recount the process of prismatic blade production. Fray Motolinia, a Spanish observer, recorded: The production of prismatic blades creates not only a very standardized final product, but also a standardized waste assemblage. The analysis of obsidian

debitage In archaeology, debitage is all the material produced during the process of lithic reduction – the production of stone tools and weapons by knapping stone. This Assemblage (archaeology), assemblage may include the different kinds of lithic fla ...

can reveal whether or not prismatic blade production occurred at a site and, if it had, what stages of production the process included. In other words, the types of manufacturing waste present (e.g., rejuvenation flakes and/or blades, platform rejuvenation flakes, etc.) at a site can inform archaeologists about the stage in which blades were being produced.Clark (1997)

Notes

References

* Clark, John E. (1997) Prismatic blademaking, craftsmanship, and production: an analysis of obsidian refuse from Ojo de Agua, Chiapas, Mexico. ''Ancient Mesoamerica'' 8:137-159. * Clark, John E., and Douglas D. Bryant (1997) Technological typology of prismatic blades and debitage from Ojo de Agua, Chiapas, Mexico. ''Ancient Mesoamerica'' 8: 111–136. *Hester, Thomas R., Robert N. Jack and Robert F. Heizer. The Obsidian of Tres Zapotes, Veracruz, Mexico. University of California Archeology Research Facility. No. 13 pp. 65–131, 1971. {{DEFAULTSORT:Prismatic Blade Archaeological artefact types Lithics Mesoamerican artifacts Stone objects