The geological formation of bedrock, the effects of weathering, and the petrological structure and texture of rocks all have a major influence on the physical properties of aggregates. When planning a concrete construction project, it is important to understand the different classifications of aggregates. Rocks are typically classified as igneous, sedimentary, or metamorphic based on their formation over long periods of geologic time. However, common multivariate statistical methods used in chemometric studies, such as linear discriminant analysis, do not lead to satisfactory classification error rates. Classification of aggregates is usually based on their geological origin, size, shape, unit weight, and other factors.
Depending on the shape of the particles, aggregates can be rounded, irregular or partially rounded, angular or scaly. Approximation is analyzed in terms of its classification properties using Mahalanobis distance or flexible discriminant analysis. Near and medium infrared spectra can also be used to statistically classify different petrographic varieties of aggregates. Aggregates can be classified as natural or crushed depending on their source and production technique. Infrared spectroscopy is a reliable tool for quantitative and qualitative analysis of minerals.
However, rock classification is complicated by the fact that the optical behavior of the minerals that form the rock often appears dull.