Frequency Distributions in Accessory Mineral Analysis

Counts to determine the frequency distributions of the occurrence of accessory heavy minerals in sediments may lead to binomial, Poisson, or negative binomial distributions; and conditions leading to those distributions are discussed. A set of data may be "fitted" to these model distributions, and the goodness of fit may be tested by chi-square. An example of fitting the Poisson, mixed Poisson, and negative binomial to some estimates of the frequency of zircon in some samples of Oswego sandstone from a single outcrop is described; the lack of fit appears to be due to non-random variation among operator-sample pairs.