Bulk samples are employed where the question is the level of crystalline silica in a product. Usually, there is little difficulty obtaining sufficient sample for the analysis, and the sample can reasonably represent the product if the sampling procedure followed good statistical practices. The preparation of bulk samples is an art that is not easy to master. The biggest single problem is preferred orientation of the crystallites in the sample. Calvert et al.
Side drifting and spheroidizing are the most successful.
If there is sufficient sample, usually several grams, then the spheroidizing approach may be employed. Bulk samples require absorption corrections or the use of one of the reference methods. All the theory is derived for the infinitely thick sample, and a thinner sample presents additional correction problems. Calibrations based on an intensity response for quartz compositions in standard samples would have to be applied carefully. If the matrix absorption effects are matched, the standard curve can apply.