Root Beer Flint

Root Beer flint is the name modern flintknappers have given to a variety of chert that is distinctive and widespread in central Texas.  It is perhaps most abundant in Kimble and Kerr Counties, but also occurs in several adjacent counties.  Similar materials of slightly different coloration occur as far east as Comal County and as far north as the Callahan Divide (just south of Abilene).  As the name implies, classic examples of this flint resemble the color of the beverage root beer – dark brown or grayish brown and translucent on thin edges. In fact, there is considerable color variation within the general and informal designation, Root Beer flint. One notable variant resembles chocolate milk, while another has maroon coloration that sometimes includes an unusual shade of dark blue.  Color variation is often created by 'swirl' patterns of different grain textures, although the best pieces are homogenous, dark and translucent.

Root Beer flint often occurs in lag deposits on mesas, divides, and upland plains; such deposits were left behind hundreds of thousands of years ago by ancient rivers and streams.  It also occurs frequently as outcrops in primary context within limestone bedrock formations, and can be found in secondary context in the gravel beds of many streams of the region such as the Llano River.  The primary context deposits occur in the Segovia and Fort Terrett geological formation “members” of Lower Cretaceous limestone.  Similar material, such as that found in Comal County, occur in different Lower Cretaceous limestone formations. 

Because it was widespread, abundant, and of generally good quality, Root Beer flint was an important tool stone for native flintknappers.  This flint most commonly occurs as thin, flat cobbles or “slabs” and these are often quite large, with pieces from 12 to 18 inches in length not at all unusual.  The flint typically has a thin white to orange colored cortex (outer rind).  There are many upland quarry sites in the region--places where the flint is concentrated on or just under the surface and where native flintknappers returned many times to acquire tool stone. Aboriginal knappers had a particular method for reducing the large flat cobbles, or slabs found in upland lag deposits.  Many of the cobbles are between 1.5-4 inches (4-10 centimeters) in thickness, and it is common for the innermost portion to be of poor quality.  Therefore, the knappers would remove only large flakes from the outer veneer of superior Root Beer flint and discard the cobble.  A few large flakes often were removed from both faces of the flat cobbles, leaving bifacial cores that usually were not used again. 

At its best, Root Beer flint is a homogeneous material of good quality.  It is glassy and translucent, but has a toughness that makes it less brittle than Georgetown flint, for example.  One advantage of this quality is that Root Beer flint is less prone to breakage during manufacture.  Some contemporary knappers heat treat Root Beer flint at relatively low temperatures of less than 400 degrees F because it won't tolerate the higher temperatures required to heat treat many Texas cherts.  Regarding this propensity to overheat easily, one of the top contemporary Texan knappers, Troy Herndon of Dallas, says that "Root Beer will blow up on a hot day!"  

Close icon




photo of root beer flint
Classic example of Root Beer flint. Aboriginal knappers removed several large thin flakes from this thin, flat cobble, leaving behind a large bifacial core. They were obviously after the best part – the thin layer of top-quality material sandwiched between the thin cortex (orange-white outer layer) and the inner central mass of mediocre quality flint. The large thin flakes they took away would have been ideal for making thin bifaces and dart points. Photo by Glenn Goode.




photo of root beer flint
Thin biface or “quarry blank” showing the “swirl” pattern of contrasting grain texture commonly found in pieces of Root Beer flint.












photo of root beer flint
Group of Root Beer flint items. Clockwise from the right, these include a flat cobble, a large flake, four blades, a bifacial quarry blank, and a large flake. These are the work of archeologist and flintknapper Glenn Goode, who took these photos.





photo of root beer flint
Two abandoned bifacial cores of Root Beer flint. Aboriginal knappers removed one or several large flakes from both faces of each thin, flat cobble. Such flakes would have been quite suitable for making knives or dart points.