archaeology Archaeology or archeology is the scientific study of human activity through the recovery and analysis of material culture. The archaeological record consists of artifacts, architecture, biofacts or ecofacts, sites, and cultural landsc ...

, 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 industr ...

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 extruded from a volcano cools rapidly with minimal crystal growth. It is an igneous rock. Obsidian is produced from felsic lava, rich in the lighter elements such as silicon ...

, 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 ...

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. Flint was widely used historically 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 monocli ...

blades are not uncommon. The term is generally restricted to

Mesoamerica Mesoamerica is a historical region and cultural area in southern North America and most of Central America. It extends from approximately central Mexico through Belize, Guatemala, El Salvador, Honduras, Nicaragua, and northern Costa Rica. Wit ...

n archaeology, although some examples are found in the

Old World The "Old World" is a term for Afro-Eurasia that originated in Europe , after Europeans became aware of the existence of the Americas. It is used to contrast the continents of Africa, Europe, and Asia, which were previously thought of by thei ...

, for example in a Minoan grave in

Crete Crete ( el, Κρήτη, translit=, Modern: , Ancient: ) is the largest and most populous of the Greek islands, the 88th largest island in the world and the fifth largest island in the Mediterranean Sea, after Sicily, Sardinia, Cyprus, ...

. 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 A quadrilateral with at least one pair of parallel sides is called a trapezoid () in American and Canadian English. In British and other forms of English, it is called a trapezium (). A trapezoid is necessarily a convex quadrilateral in Eu ...

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

isosceles trapezoid In Euclidean geometry, an isosceles trapezoid (isosceles trapezium in British English) 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 defin ...

. 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 In lithic analysis, a subdivision of archaeology, a bulb of applied force (also known as a bulb of percussion or simply bulb of force) is a defining characteristic of a lithic flake. Bulb of applied force was first correctly described by Sir John E ...

(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 In lithic reduction, the striking platform is the surface on the proximal portion of a lithic flake on which the detachment blow falls;Kooyman, Brian Patrick. ''Understanding Stone Tools and Archaeological Sites''. University of Calgary Press, 2000, ...

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 extruded from a volcano cools rapidly with minimal crystal growth. It is an igneous rock. Obsidian is produced from felsic lava, rich in the lighter elements such as silicon ...

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 historic or contemporary), and which has been, or may be, investigated using the discipline of archaeology an ...

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 may include the different kinds of lithic flakes and lithic blades, bu ...

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