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Weathering Assessment of Quartz Grains: A Semiquantitative Approach¹

ABSTRACT

This paper details the development of a technique to assess the relative weathering state of quartz grains as revealed by scanning electron microscopy (SEM). This approach considers the criticisms leveled against environmental assessments based on SEM observations. The method uses only one size fraction of grains to eliminate size dependent surface texture variability. Operator bias is removed by coding specimens. A semiquantitative approach is used: five grain surface features indicative of "weathering" and five indicative of "freshness" are observed on each grain. A binary scoring system is used where a negative point is assigned for the presence of a weathering feature and a positive point is assigned for the presence of a freshness feature. A zero is assigned for each absent indicator feature. Summing the points gives the weathering class (WC) for a grain. The mean WC for 15 to 30 grains is the weathering classification for a sample. This systematic approach is an improvement over qualitative assessments and allows for statistical analysis of the data.

¹ Contribution from the Dep. of Agronomy, Univ. of Illinois, Urbana, IL 61801.

² Assistant Professor, Agronomy Dep., Univ. of Illinois, 1102 S. Goodwin Ave., Urbana, IL 61801.

Received for publication December 7, 1984. Accepted for publication April 10, 1985.