Date of this Version
Published in Transactions of the Nebraska Academy of Sciences, Volume 3 (1976).
Experiments indicate that the application of heat to silica material may have aided primitive man in the manufacture of chipped-stone implements. When quartzite from Spanish Diggings is heat treated, predictable color changes occur. Using Spanish Diggings material as a model, quartzite artifacts from the Hudson-Meng site were examined in an attempt to determine if this material was thermally altered.
Archaeologists are being confronted with the problem of identifying source areas of lithic material encountered during excavation. It is now recognized that lithic materials from some archaeological sites have been altered by heat treatment (Crabtree, 1972, p.5). This may require a revision, of current ideas regarding importation and wide scale lithic trade networks. The possibility of heat treatment also requires that the archaeologists keep in mind not only what the material is like at the source area but also the possible alterations caused by heat.
This study was carried out on quartzite from Spanish Diggings, a large quarry site in Platte Co., Wyoming (NE¼; Sec. 1: T. 30N; R. 67W). The purpose was to determine what changes, if any, occurred when these quartzites were subject to heat treatment.
A random sample of quartzite was taken from the quarry area. Fifty samples were then sorted by color (with the aid of the Munsul color chart), grain size, and banding characteristics. The colors ranged from light-to-dark yellow-browns, light-to-dark grays, purples of various shades, blacks and olive; greens.
Conditions under which heating experiments were conducted are as follows:
1. Rapid temperature increase: temperature was raised by 5O°C increments and held approximately 1 hour, at each succeeding increment up to 600°C. (no measurement for weight loss was taken)
2. Gradual temperature increase: temperature was raised by 5O°C increments and held approximately 24 hours at each succeeding increment up to 600°C. Specimens were weighed before and after heating to check weight loss.
1. Rapid cooling: specimens were subjected to room temperature at the end of the testing period.
2. Gradual cooling: specimens were left in the oven at the end of the testing period.