Friday, October 15, 2021

The Most Common Artifact Recovered from Precontact Archaeological Sites - Let’s Get Flakey

October is Archaeology Month and to celebrate, The State Museum of Pennsylvania announces its annual ‘Workshops in Archaeology’ conference to be held on Oct. 30, 2021. Due to concerns with COVID-19, this will be a virtual only event, registration is required. The topic of the Workshops this year is Hidden Stories: Uncovering African American History through Archaeology and Community Engagement. To learn more please review our previous blog post and register for this event on our web page

For additional programming please visit the Society for Pennsylvania Archaeology, the Pennsylvania Archaeological Council and the Philadelphia Archaeological Forum  . 

The Most Common Artifact Recovered from Precontact Archaeological Sites - Let’s Get Flakey

A basic guide to stone or lithic flake terminology.

        What is the most common artifact recovered from Precontact archaeological sites? Not arrowheads or spear points or pottery sherds that get all of the attention, but flakes – the  unmodified and unused by-product of chipped stone tool production. Also known as chips, detritus, spawls, shatter or over the past twenty years, most commonly labeled as debitage, these artifacts are ubiquitous at Precontact sites. They outnumber the tools by at least 100 to 1. Flakes are usually the first artifacts that are found during site surveys, and sometimes the only evidence of a Precontact occupation but they are frequently overlooked during analysis and usually lumped together as a single artifact type. Flakes are not pretty; they usually appear as relatively small slivers of rock and even the larger pieces are not readily recognizable as artifacts to the untrained eye. For a long period in archaeological research, flakes were not thought to be very useful in interpretating past cultural behavior. For example, the early collections in The State Museum of Pennsylvania from the 1920s and 1930s contain more projectile points, pottery and bone objects than flakes. Up until the 1970s, some professional archaeologists did not bother to curate flakes during otherwise systematically excavated site investigations but tossed them in the trash at the end of the day. “Flakes tell us Native Americans made stone tools – so what!”

       Based on flint knapping experiments beginning in the 1960s, (Crabtree 1972) and becoming common in the 1980s (Callahan 1979), the interest in debitage and the potential contributions to the interpretation of past cultural behavior became more common. Now, the analysis of debitage is usually a regular part of archaeological survey and site reports. These artifacts tell a great deal about the activities at sites and the tools that were being made and as John Whittaker (1994:21) observes, the occupants of a site were “so inconsiderate as to take the useful tools away” so in many cases the flakes are the only evidence to interpret the past.  

Typical core and flake (image from Whittaker 1994)

The literature is now voluminous, and the following will serve as an introductory or basic guide to the terminology used in describing flakes and the analysis of debitage. All flakes are not the same, but they share certain characteristics. Let’s begin with some terminology. The block of stone to be hit is called the core (to the left in the above illustration) and the pieces that fly off are the flakes (to right). Basically, when a hammerstone hits the edge of a core, the force of the hammer is transmitted into the core; energy is most pronounced at the point of impact and gradually dissipates outwardly to the distal end of the flake. The interior surface of the flake, facing the core is the ventral surface. The exterior side of the flake facing out is called the dorsal surface. At or just below the point of percussion, also known as the striking platform, there is a swelling on the ventral surface known as the bulb of percussion. Further down the ventral surface of the flake are ripple marks. On the dorsal surface there are flake scars where previous flakes were removed from the core. These are characteristics found on stone that was broken for stone tool production; they are not commonly found on stone that broke through natural processes.  

A microcore for the production of razor-like blades  (Photo from the Section of Archaeology, The State Museum of Pennsylvania)

Image of a flake illustrating the point of percussion or striking platform, the bulb of percussion, ripples and exterior flake scars. (Image from Whittaker 1994) 

In a sense, making stone tools is comparable to a wood carver whittling wood. It is a subtractive process, beginning with an amorphous shaped natural block of stone and ending with a finished tool. The process of making stone tools is called knapping or more commonly, flint knapping. Knappers use a stone where it is possible to predict the manner in which it breaks. Just as important, knappers must be able to control the break so that tools can be shaped. The characteristics of the lithic material typically used to make chipped stone tools, also known as “toolstone”, is that they are relatively hard, brittle, plastic and homogeneous, containing few impurities. This type of stone breaks with a conchoidal fracture (cone shaped) similar to a bee bee shot through a windowpane. Flakes usually exhibit a subtle curve in one or more directions. In Pennsylvania the most common lithic materials used in the production of chipped stone tools are chert, jasper, quartz, quartzite, argillite and metarhyolite.

         Knapping usually requires three different types of tools to break the stone - two types of hammers and a pointed piece of antler. An
abrading stone is used to prepare and shape the striking platform so that flakes can be more easily and precisely removed. The hard hammer is for breaking up the blocks of stone from the quarry into manageable blanks. These may range in size from a baseball to a bowling ball weighing ten pounds or more. A soft hammer or baton is usually made from antler (moose or elk) or hard wood (ash or hickory) measuring less than a foot in length. These are for thinning the blanks into nearly finished pieces. The final sharpening and shaping is usually performed with a pressure flaker, commonly made from antler. The point of the antler is placed on the edge of the tool and small flakes are pressed off rather than struck. This is the most precise technique of flake removal.

Flint knapping tools (Photo from the Section of Archaeology, The State Museum of Pennsylvania)

Using a hammerstone on a large flake with other knapping tools in foreground (Photo from the Section of Archaeology, The State Museum of Pennsylvania)

Pressure flaking using a pointed antler. (Image from Whittaker 1994)

Pressure flaking the base of a spear point (Photo from the Section of Archaeology, The State Museum of Pennsylvania)

The key to the analysis of debitage is that the hammerstone, the baton and the pressure flaker all produce different shapes of flakes and therefore the different technological activities can generally be identified. Hammerstone flakes are relatively thick and especially the bulb of percussion is pronounced. Hammerstone flakes are generally produced during the initial stages of tool production, so they have fewer flake scars on their dorsal surface and even less evidence of previous flaking and grinding on the striking platform. Baton flakes are relatively thin, and the bulb of percussion is diffused as the percussion blow spreads out evenly below the striking platform. There are usually many flake scars on the dorsal surface coming from multiple  directions and the striking platform shows evidence of grinding and pressure flaking so the flake can be removed more precisely. In addition, when working a biface (a biface is worked on both flat surfaces of the stone), such as a knife or spear points, baton flakes frequently exhibit a distinctive lip on the striking platform. This is a remanent product of the tool edge that offers evidence of the thickness and size of the tool. Pressure flakes are smaller, usually less than ¾ of an inch in length and thin, often with parallel sides and the striking platform is usually more heavily ground for better attachment.

A baton flake illustrating the lip on the platform, the diffuse bulb and numerous flake scars. (Image from Whittaker 1994)

Complicating the analysis of debitage is that less than half of the flakes are normally complete; most are broken in some fashion and therefore the striking platform or bulb of percussion is missing, something not very useful in the analysis of debitage. In addition, these characteristics or attributes are somewhat subjective, and identifying these traits is very time consuming. However, when applied to large collections, the attribute analysis of debitage can be useful in distinguishing different kinds of knapping activities at a site. Identifying the location of early stone tool production, the location of actual tool production areas, the final sharpening and shaping of tools, and the resharpening of tools can be valuable information in the interpretation of activities at a site.

There are other types of flakes that define more specific technological activities such as blade flakes, biface thinning flakes, overshot flakes, bipolar flakes, and platform rejuvenation flakes and these can be the topic of future blogs.  

The foregoing methodology is based on the identification of specific attributes on flakes. Especially, as large state and federal projects in compliance with the National Historic Preservation Act became more common, archaeologists became more concerned with the accuracy of the attribute analysis but also the time involved in flake analysis. In response, a variety of alternative methods have been developed. Generally, these fall under the term aggregate analysis and involve sorting flakes by size using a series of graduated sieves (screens). Needless to say, these other methods are complicated and there is not sufficient space to describe them all here. Spoiler alert, it is generally agreed that the best results are achieved using a combination of attribute analysis and aggregate analysis (Hall and Larson 2004).  

As noted by Jeffery Rasic, considering the high frequency of flakes at sites, they are “one of the primary sources of information about human behavior … being able to reconstruction technological behaviors related to production, use, transport, and maintenance of stone tools … these data and interpretations, in turn can shed light on questions of broader anthropological concern such as the ways people organize their work, subsistence activities, travels, and social and political behavior” (Rasic 2004:114). Many studies have demonstrated that debitage at sites changes during different time periods suggesting that debitage reflects the basic characteristics of the cultural adaptation (Parry 1994).

 We hope you have enjoyed this brief overview of debitage terminology and more carefully examine the next flake you find realizing that it has an interesting story to tell. Please visit our gallery at The State Museum of Pennsylvania to see examples of stone tool production by the Indigenous peoples who developed and perfected this technology.  We also invite you to visit our on-line collections.



Callahan, Errett

1979    The Basics of Biface Knapping in the Eastern Fluted Point Tradition: A Manual for Flintknappers and Lithic Analysts. Archaeology of Eastern North America 7:1-180.


Crabtree, Don E.

1972    An Introduction to Flintworking. Occasional Papers no. 28. Pocatello: Idaho State University Museum.


Hall, Christopher T. and Mary Lou Larson

2004    Aggregate Analysis in Chipped Stone. The University of Utah Press, Salt Lake City.


Parry, William

1994    Prismatic Blade Technologies in North America. In The Organization of North American Prehistoric Chipped Stone Tool Technologies, edited by P. J. Carr, pp. 87-98. Archaeological Series No. 7, International Monographs in Prehistory, Ann Arbor.


Rasic, Jeffrey T.

2004    Debitage Taphonomy. In Aggregate Analysis in Chipped Stone, edited by Christopher T. Hall and Mary Lou Larson, pp. 112-135. The University of Utah Press, Salt Lake City.


Whittaker, John C.

1994    Flintknapping: Making and Understanding Stone Tools. University of Texas Press, Austin.


For more information, visit or the Hall of Anthropology and Archaeology at The State Museum of Pennsylvania .

Monday, September 20, 2021

Don't Miss the 2021 Annual Workshops in Archaeology

October is Archaeology Month and to celebrate, The State Museum of Pennsylvania announces its annual ‘Workshops in Archaeology’ conference to be held on October 30, 2021. The topic of the Workshops this year is Hidden Stories: Uncovering African American History through Archaeology and Community Engagement. This year’s workshops will be held in-person at The State Museum in Harrisburg, PA and will also be offered in an online format due to the continuing COVID-19 pandemic.

The lives and activities of African Americans during the 18
th and 19th centuries are poorly documented in the historic record and frequently biased. In addition, the contributions of enslaved, indentured, and free African Americans are missing from our history books and museums. Archaeology is a method that can be used to fill this gap in our understanding of past cultural behavior in the Commonwealth. This year’s Workshops in Archaeology program will feature an overview of African American archaeological investigations and community archaeology projects in the region. Community archaeology is the practice of archaeological research in which at every step in a project, at least partial control remains with the community. These Workshops are an opportunity for archaeologists to share information and for the community to provide input on the future of African American community archaeology in Pennsylvania.

Map showing the major routes of the Underground Railroad through Pennsylvania.

Countless untold stories of the lives of early African Americans in Pennsylvania are waiting to be uncovered. For the most part, these stories have not been told in history classes and are not discussed in textbooks. From the Old 8th Ward neighborhood of Harrisburg, which was demolished to make way for the expansion of the Pennsylvania State Capitol grounds, to the communities of Yellow Hill near Gettysburg and Six Penny Creek in Berks County that were established by free and formerly enslaved African Americas, these stories should not be forgotten. In many towns, cemeteries that were once an important part of community life have been lost or had their markers intentionally removed, leaving the descendants of those interred wondering where their ancestor’s remains may lie. In other places, the daily lives of both the average person and those making important contributions to society lie equally unexplored. 

Old 8th Ward section of Harrisburg prior to demolition
(PA State Archives, RG-17, Series 522; image: PHMC)

Community archaeology seeks to bring some of these stories to life by uniting professional archaeologists, historians, members of the public, and those with a vested interest in African American history and heritage.  This year’s Workshops will look at recent projects by professional archaeologists and historians at sites around Pennsylvania and the Mid-Atlantic region, as well as ongoing grassroots preservation efforts.  

Our featured Keynote Speaker will be Dr. Cheryl LaRoche, professor in the American Studies Department at the University of Maryland. Dr. LaRoche is involved in the study of 18
th and 19th century free black communities and their relationships to the Underground Railroad. She has consulted on projects for the National Park Service, the African American Museum of Philadelphia, the Smithsonian, and other institutions and worked with the PBS series ‘Time Team America’ in the search for the Josiah Henson House in Maryland. Dr. LaRoche’s 2014 book Free Black Communities and the Underground Railroad: The Geography of Resistance explores the Underground Railroad using archaeology and focuses on the free black communities that assisted in the escape of fugitives from slavery. She will be speaking on Community Archaeology and her ongoing work in this field.

At the President’s House site in Philadelphia Dr. LaRoche and Doug Mooney discussing the archaeology and heritage uncovered at this site.

The program includes presentation from the following;

·       Dr. Alexandra Jones - professor and member of the Society of Black Archaeologists, founder of the nonprofit organization Archaeology in the Community. Dr. Jones will be providing an Introduction to Community Archaeology:

·       Barbara Barksdale – historian and caretaker of the African American Midland Cemetery in Steelton, PA, will speak on The Hallowed Ground Project in Pennsylvania, highlighting the identification and preservation of cemeteries containing Civil War-era United States Colored Troops:

·        Samantha Taylor – archaeologist with New South Associates, discussing The Role of Archaeology in Bridging Informational Gaps Between Diasporic Communities: A Case Study at Pandenarium, Mercer County, Pennsylvania and how work at this site is changing perceptions and helping in its preservation:

·       Wade Catts – archaeologist at South River Heritage Consulting, The Perkins-Dennis farm presentation will explore how investigations at this historic site are sharing the story of free African Americans in the north: A Gift to the Nation: The Perkins-Dennis Farm, an African American Farm in Pennsylvania’s Northern Tier:

·       Douglas Mooney – archaeologist with AECOM, discussing important sites in the city of Philadelphia, including the National Constitution Center, the President’s House, and Bethel Burying Ground, African American Archaeology in Philadelphia:

·       Erik Kreusch - Archaeologist/Compliance Coordinator at Gettysburg National Military Park, The National Park Service (NPS). This presentation will highlight efforts being made by the NPS to improve upon and diversify the park narratives through historic and archaeological research.

·       Matthew Reeves – Director of Archaeology at Montpelier Plantation in Virginia, home of President James Madison, speaking on Communities Reclaiming Ancestral Lands through Public Archaeology: A case study from a presidential plantation: and,

·       Angela Jaillet-Wentling – Cultural Resources Program Coordinator for DCNR Bureau of State Parks, presenting new interpretations of the Pandenarium site and the lessons learned that can apply to future work in this field, Telling Untold Stories of Underrepresented Populations.

 In addition to the presentations, archaeologists from the State Historic Preservation Office (SHPO) will be present during break periods to help those who wish to record a site as well as curators from the Section of Archaeology who will be assisting with the identification of artifacts. Bring in your historic or prehistoric artifacts for identification and analyses by the experts.

Archaeologists from the SHPO office and Section of Archaeology will be on hand to assist with artifact identification and recording of archaeological sites (image: PHMC) 

A panel discussion with the presenters on The Future of African American Community Archaeology in Pennsylvania and a wine and cheese reception will wrap up the day’s activities.

Suggested donation for the Workshops is $25.00. Sessions will be available virtually via Zoom, registration is required for both the in person and virtual program. Once you are registered, attendees will receive a link and password for the sessions listed. Please visit The State Museum of Pennsylvania site to register.

Please mark your calendar and plan to join us on October 30th either in person at The State Museum or on-line in our virtual program.  Check our blog and the listed web sites for program information updates and registration links.  The Society for Pennsylvania Archaeology (SPA) will post events occurring for Archaeology Month throughout the region on their website.  

For more information, visit or the Hall of Anthropology and Archaeology at The State Museum of Pennsylvania .

Monday, August 23, 2021

Shining a Light on Radioactive Uranium Glass

This week’s blog focus is uranium glass (also called Vaseline or canary glass). Although seemingly non-descript under incandescent lighting, these objects fluoresce brilliantly when viewed under an ultraviolet black light. The glow produced by these objects is a result of the colorant used in the vessels – uranium. Uranium glass was widely popular and was produced by several Pennsylvania glass manufacturers. While using uranium glass for food consumption is not recommended, they usually pose little danger to people.

Photo by Melanie Mayhew (private collection)

The hidden properties of uranium glass are revealed under a black light.

Uranium was formally discovered over 220 years ago by German chemist Martin Klaproth. Klaproth named this element “uran” after the planet Uranus. As with the discovery of other brightly colored compounds and elements, uranium soon became a popular pigment. The first documented use as a glass colorant was recorded in 1817 (Lole 1995). Its popularity as a colorant in Europe later spread to the United States and Japan. Natural uranium was used to color glass, enamels, and ceramic glazes until the 1940s when the onset of World War II resulted in a production gap of uranium-containing housewares. Depleted uranium was made available for use beginning in 1959. Although uranium use as a colorant has decreased dramatically in recent decades, some contemporary objects claiming to contain uranium can still be found for sale online.

Photo by Andrew Silver, USGS, Public domain, via Wikimedia Commons

The natural yellow to green color of uranium ore led to the widespread use of this material as a colorant.

Uranium glass is most frequently associated with yellow to yellow-green colors, but fluorescent objects were later made in a range of colors. There is a lack of awareness around the widespread use of uranium colorants (Strahan 2001), possibly because without a black light or specialized knowledge of uranium colorants, identification by archaeologists can be easily missed. Archaeologists use several observational methods to identify and classify artifacts, and a UV light is a useful tool to assist with the identification of objects containing radioactive colorants. The Corning Museum of Glass identifies several other components used in glass manufacture that may also fluoresce, such as antimony (light pink or pink-orange), manganese (yellow), and glass with a high lead content (bluish white).

Photos by Wombat1138, Public Domain via Wikimedia Commons

Glass objects containing radioactive material have been made in a range of colors, making their identification more difficult.

Pennsylvania's rich resources, including sand, coal, and flint, contributed to its importance as a glass manufacturer. By the time of the Civil War, Pittsburgh, Pennsylvania was the premier city for glassworks in the United States. Many glass manufacturers in Pittsburgh produced a range of uranium glass housewares to satisfy consumer demand at the turn of the 20th century.

For those with a fondness for these objects, the Environmental Protection Agency (EPA) indicates there is usually little health risk involved with keeping antiques containing radioactive materials, if they are in good condition. Moreover, an additional source indicates little health risk unless objects are stored in a small area, are used to store and consume large quantities of acidic or alkaline foods, or if the object must be drilled for conservation work thus creating a dust from the removed material (Strahan 2001).

We hope you have enjoyed this blog on the hidden properties of uranium glass. We invite you to explore related objects by searching for the popular term “Vaseline glass” in the Pennsylvania Historical and Museum Commission’s online collections database.

Argonne National Laboratory

N.D.       Uranium Quick Facts. Depleted UF6 Guide., accessed August 10, 2021.

Corning Museum of Glass

N.D.       Conservation Laboratory. Conservation., accessed August 10, 2021.

Environmental Protection Agency (EPA)

N.D.       Radioactivity in Antiques. Radtown., accessed August 10, 2021

Heinz History Center

N.D.       Glass: Shattering Notions. Exhibits., accessed August 10, 2021

Lole, F. Peter

1995      Uranium Glass in 1817- A Pre-Riedel Record. Journal of Glass Studies 37:139-140.

Strahan, Donna

2001      Uranium in Glass, Glazes and Enamels: History, Identification and Handling. Studies in Conservation 46(3):181-195

For more information, visit or the Hall of Anthropology and Archaeology at The State Museum of Pennsylvania .