1.1 This guide outlines procedures for the petrographic examination of samples representative of materials proposed for use as aggregates in concrete. 1.2 This guide outlines the extent to which petrographic techniques should be used, the selection of properties that should be looked for, and the manner in which such techniques may be employed in the examination of samples of aggregates for concrete. 1.3 This guide does not attempt to describe the techniques of petrographic work since it is assumed that the guide will be used by persons who are qualified by education and experience to employ such techniques for the recognition of the characteristic properties of rocks and minerals and to describe and classify the constituents of an aggregate sample. 1.4 The rock and mineral names given in Descriptive Nomenclature C294 should be used insofar as they are appropriate in reports prepared according to this guide. 1.5 This standard does not purport to address the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 1.6 The values stated in SI units are to be regarded as the standard.