All That Glitters Is Not Gold (and Not All Brown Cherts Are Knife River)

All That Glitters is Not Gold

(And Not All Brown Cherts Are Knife River)

by John Bradford Branney

 

Figure One - 3.8-inch-long Besant knife form made from Knife River and surface found
on private land near New Town, North Dakota by Sherry Christianson.
Note color, white/yellow splotches, plant fossils, loose hinges, and patina.
John Bradford Branney Collection. 

I am an artifact hunter and prehistorian who spends much of my spare time hunting rocks on the high plains of Wyoming and Colorado. When I think about the most popular raw materials for toolmaking during high plains prehistory, I think of beautiful Hartville Uplift Jasper or Spanish Diggings Quartzite or Flattop Chalcedony, or the subject of this article: Knife River Chalcedony. I would be remiss if I did not mention that there were literally hundreds of different types of raw materials from Alberta, Canada to the Panhandle of Texas for prehistoric people to choose from. Some of those raw materials have local or regional names such as Big Horn Chert or Pryor Creek Jasper or Black Forest Silicified Wood while other raw materials just go by a generic rock type name such as moss agate, tiger chert, or caramel-colored jasper. Maybe someday I will write an article about the less glamorous high plains raw materials. 

Figure Two - BEYOND the CAMPFIRE, the fifth book in the
SHADOWS on the TRAIL Pentology. 

Based on archaeological evidence, it is clear that prehistoric people sought the highest quality raw material that was available to make their tools and projectile points. The ideal raw material fractured conchoidally in a predictable manner and was not too soft or brittle to hold a sharp working edge. Besides availability and quality, a rock type’s flashiness was also a factor for prehistoric people. Knife River Chalcedony checks all the boxes; it was available and of high quality, and it was definitely beautiful. Based on archaeological evidence, prehistoric people went out of their way to scavenge and use Knife River Chalcedony.

You will notice that I called Knife River a chalcedony, but Luedtke (1992:6) would argue with my definition. Luedtke pointed out that chalcedony is the only variety of chert that scientists can identify microscopically by its fibrous form. Those fibers cannot be seen with the naked eye. Luedtke proclaimed that while most cherts made from chalcedony were translucent, not all translucent cherts were chalcedony. She added that Knife River was the perfect example of a translucent chert that was not a chalcedony but a granular quartz, and not a fibrous quartz.

 

Figure Three - Note Knife River translucency on this 2.5-inch-long Middle Archaic Oxbow
Knife Form surface found on private land near Gillette, Wyoming by Chuck Carlson.
John Bradford Branney Collection.   

The most popular name for Knife River Chalcedony by far and used by archaeologists and collectors alike is Knife River Flint which is oftentimes abbreviated as KRF. According to Luedtke (1992:140), the definition of flint is a “homogenous, high quality chert, especially the dark gray or black cherts that form in the Cretaceous chalks of Europe”. That does not fit Knife River any more than the definition of chalcedony does. The most accurate name is probably Knife River Chert because the term chert casts a wide net by including most varieties of microcrystalline quartz.

Since an old habit is hard to break, I will refer to the rock type as either Knife River Chalcedony or just plain Knife River for this article. Secondly, I will refer to Knife River Chalcedony as semi-translucent even though some authors prefer to call it translucent. When I think of something translucent, I think of a clear pane of glass, and Knife River is not as translucent as a clear pane of glass.   

Luedtke (1992:6) described Knife River as a very dark brown, fine-textured, silicified lignite with a medium luster and a depth of translucency from 5 to 11 mm. Bates and Jackson (1984:295) defined lignite as a brownish-black coal that was intermediate in coalification between peat and sub-bituminous coal. The adjective silicified describes a process where organic matter, in this case lignite, became saturated and replaced by silica in the form of quartz, chalcedony, or opal.  

Figure Four - 2.8-inch-long Goshen spear/knife form surface found on private land in the 
Sand Hills of Lincoln County, Nebraska. John Bradford Branney Collection.  

Kristensen et al. (2018:22) analyzed Knife River using macroscopic, microscopic, and geochemical techniques and supported the description that the rock type was silicified lignite. The authors described the color of Knife River as blonde to dark coffee brown and stated that the rock type could possess high translucency, visible bedding planes, plant microfossils, and white splotches. The authors also declared that by just using visual inspection, Knife River could not be discerned from silicified peat or chalcedony.

Geologists know very little about the origin of Knife River Chalcedony because it is only found in secondary deposits and not in its original geological context. Hickey (1966:64-5) suggested that based on its high carbon content, plant fossils, and proximity to unsilicified lignite, Knife River originally formed as a deposit of organic lignite in the Eocene geological period. He surmised that later in the Oligocene geological period, silica-rich groundwater saturated the lignite, creating a hard silicified lignite layer. Kristensen et al. (2018:3) reported that by the time Paleoindians showed up to exploit the rock type in the late Pleistocene geological period, the silicified lignite bed was eroded away and broken up into pebbles, boulders and cobbles of Knife River.  

Figure Five - Knife River nodules found in secondary geological contexts from eroded bedrock outcrops that no longer exist. The images on the left and top right are courtesy
of David McDonald. The bottom image on the right is courtesy 
of the Archaeology and Historic Preservation Division, 
State Historical Society of North Dakota.

Clayton et al. (1970) expanded on that interpretation by postulating that the original Knife River lignite bed was initially surrounded by the clays, silts, and sands of the Golden Valley Formation of Eocene age and underlain by the clays, silts, sands, and lignite beds of the Sentinel Butte Formation. Earlier, Benson (1949, 1952) informally divided the Golden Valley Formation into two members, a brightly colored claystone called the Bear Den Member of Paleocene age, and an overlying unit called the Camels Butte Member of Eocene age. Both members were deposited roughly between 50 and 57 million years ago.

Knife River’s color is often compared to “root beer, coffee, or beer bottle” with a touch of translucency. Many prehistoric artifacts made from Knife River are beautiful and glow in vivid shades of brown when backlit (figure three). I have seen collectors pay a pretty penny for prehistoric artifacts made from a desirable chunk of Knife River raw material. Market demand combined with a plethora of lookalike materials from Texas to Alberta led to the overidentification of Knife River as the raw material. Collectors and archaeologists must be careful when they use visual inspection alone to identify Knife River from other semi-translucent brown cherts or chalcedonies.

Figure Six - Agate Basin spear/knife forms made from semi-translucent to opaque Knife River 
and surface found on private land from North Dakota to northern Colorado. These
examples show color variation, white splotches, hanging hinges, and patina.  
The longest Agate Basin is 4.7-inches-long.
John Bradford Branney Collection.  

I have quite a few prehistoric artifacts in my collection made from Knife River Chalcedony, found from the Dakotas and Montana through Wyoming and south to northern Colorado. The artifacts range in color from very dark brown to honey-colored brown. Most of my Knife River artifacts exhibit a certain degree of translucency, but I have a couple of nice examples that are completely opaque. When I visually inspect an artifact, I use five characteristics to identify Knife River. The first characteristic is its color as described in a few sentences above. The second characteristic is the silicified plant fossils or palm fronds captured in the matrix of the rock. The third characteristic is a distinctive white-to-yellow patina caused by chemical weathering and commonly found on Knife River artifacts. The fourth characteristic is the distinctive white and yellow opaque splotches on the surface of the rock or locked into the matrix. The fifth characteristic that cannot be used as a diagnostic feature for Knife River but is quite common on Knife River artifacts is loose hinge fractures, even when the artifact was found in freeze-thaw country.  I have examples of Knife River artifacts with all five characteristics and I have suspected Knife River artifacts with none of those characteristics. If a person does not notice at least one of those characteristics, they might be looking at a Knife River lookalike.     

A few artifact collectors and authenticators believe that UV irradiation can be effectively used to identify Knife River as the rock type and for authenticating Knife River artifacts. That theory contends that authentic Knife River artifacts fluoresce under either short or long-wave UV light. The assumption is that authentic artifacts are aged and chemically weathered therefore they fluoresce, while the fresh surfaces on artifact reproductions won’t fluoresce. One authenticator even told me that authentic Knife River artifacts emit an orangish color under UV light when they are authentic. To test that theory, I did my own experimentation with a few of my Knife River artifacts. I did not obtain the same results as the authenticator. Of the artifacts that did fluoresce, some appeared slightly orange while others appeared almost white or some shade in between. A few artifacts fluoresced so weakly that I needed my imagination to see any fluorescence, and a few artifacts did not fluoresce at all. To ensure that the Knife River artifacts did not need to be a certain age to fluoresce, I experimented with artifacts ranging from Paleoindian to Late Prehistoric times. I concluded that using UV irradiation as a method for determining rock type or authentication of Knife River artifacts was indefinite at best.

Figure Seven - Lookalike material or Knife River Chalcedony? Several professionals and 
collectors have looked at this 1.8-inch long Folsom dart point, both macroscopically and 
microscopically and we have a hung jury on whether it is Knife River or not. 
John Bradford Branney Collection.  

Kirchmeir (2011:27) and Kristensen et al. (2018:14) experimented and determined similar results with UV radiation and Knife River. The investigators noted that artifacts made from similar materials, such as brown chalcedony and silicified peat, fluoresced in a similar manner as Knife River. In their studies, Knife River and lookalike materials showed such a wide range of fluorescence to non-fluorescence that the process was not useful for the identification of the raw material. The investigators warned that chemical weathering of the rock could enhance or obscure its fluorescence. Their conclusion was that UV irradiation was not an effective standalone technique for the identification of Knife River and should only be used in concert with other macroscopic, microscopic, and geochemical analyses.

What separated Knife River from most high plains raw materials were its overall abundance and wide distribution. The archaeological evidence that Knife River traveled far from its source during prehistoric times is overwhelming. The rock type originated from a network of rock quarries in North Dakota that supplied a vast amount of tool stone for prehistoric humans for thousands of years. Knife River’s popularity is reflected in the number of prehistoric tools made from it, the quarries’ endurance over prehistoric times, and the rock type’s dispersal across the plains.

Ahler (1986:105) estimated that prehistoric people quarried around 12.5 million kilograms (20,393 tons) of Knife River Chalcedony from roughly thirty quarry sites in a primary source area of approximately 2,000 square kilometers (772 square miles) in Dunn and Mercer Counties in North Dakota. From his estimates, Ahler calculated that prehistoric people made around 640 million tools and cores from Knife River and spread those tools and cores over an area of approximately 3.7 million square kilometers (1.4 million square miles). Whether Ahler’s estimations were accurate or not we will never know for sure, but even if we divide Ahler’s estimates by a factor of twenty, the numbers remain staggering. Knife River Chalcedony was quite popular with the prehistoric folks!

 

Figure Eight - Lookalike material or Knife River? This root-beer colored Scottsbluff point was 
surface found on private land near Green River, Wyoming. Artifact authenticator Greg Perino
identified the material as Knife River, but it could be one of the local brown chalcedonies
found in that region. The point is 2.5-inches-long. John Bradford Branney Collection.       

Steuber (2018) addressed the wide distribution of Knife River by determining whether or not archaeologists and collectors were overidentifying Knife River on the high plains. She challenged the entrenched professional view that Knife River was the dominant material in Besant/Sonota prehistoric cultural sites on the Northern Plains. Steuber chemically analyzed twelve brown chalcedony sources across three Canadian Provinces and three American States. She then compared her chemical analysis with material labeled as Knife River at archaeological sites. She concluded that Knife River was not the dominant lithic raw material at those archaeological sites after all and that the prehistoric inhabitants were exploiting local varieties of brown chalcedonies and not as much Knife River as previously reported. Steuber concluded her analysis by quoting, “All artifacts made from brown chalcedony should be referred to as such and not as KRF unless they have been previously geochemically characterized”.  

I have discovered several prehistoric rock quarries and mining operations in my search for prehistoric artifacts on the high plains and I can conclude that while the raw materials at those quarries met the knapping and durability requirements for toolmaking, the distribution never came close to the Knife River supply chain. Knife River Chalcedony was one of the kings of high plains raw material for thousands of years.      

References Cited

Ahler, S.A. 1986. Knife River Flint Quarries: Excavations at Site 32DU508. State Historical Society of North Dakota, Bismarck, North Dakota.

Bates, Robert L. and Julia A. Jackson. 1984. Dictionary of Geological Terms. Third Edition. Anchor Press/Doubleday. New York.

Benson, W.E. and Laird, W.M., 1947, Eocene of North Dakota: abstract, Geological Society of America Bulletin, v 58, p. 1166-1167.

Benson, W.E., 1952, Geology of the Knife River area, North Dakota: U.S. Geological Survey Open-File Report, 276 p.

Clayton, L., W.B. Bickley, Jr., and W.J. Stone. 1970. Knife River Flint. Plains Anthropologist 15:282-290.

Hickey, L.J. 1966. The Paleobotany and Stratigraphy of the Golden Valley Formation in Western North Dakota. Ph.D. dissertation, Department of Geology, Princeton University, Princeton, New Jersey.

Kirchmeir, P.F.R. 2011. A Knife River Flint Identification Model and its Application to Three Alberta Ecozone Archaeological Assemblages. M.A. thesis, Department of Anthropology, University of Alberta, Edmonton, Alberta

Kristensen, Todd, Emily Moffat, M. John, M. Duke, Andrew J. Locock, Cody Sharphead, and John W. Ives. 2018. Identifying Knife River Flint in Alberta: A silicified lignite toolstone from North Dakota. Occasional Paper No. 38. Archaeological Survey of Alberta.  

Luedtke, Barbara E. 1992. An Archaeologist’s Guide to Chert and Flint. Archaeological Research Tools 7. Institute of Archaeology. University of California, Los Angeles. 

Steuber, Karin Ingrid. 2018. Geochemical Characterization of Brown Chalcedony during the Besant/Sonota Period. Ph.D. Dissertation. Department of Archaeology & Anthropology, University of Saskatchewan, Saskatoon.

About the Author

John Bradford Branney has hunted and collected artifacts for six decades and he has written about his adventures for around three decades. Join Author Branney for his high plains saga about the lives of Paleoindians some twelve thousand years ago in the SHADOWS on the TRAIL Pentalogy. His books are available on Amazon.com or wherever fine books are sold.