AS 1141.26:2019 Methods for sampling and testing aggregates
7  Procedure
Determination of the secondary mineral content of rock specimens requires the analyst to hold a bachelor’s degree in geology or earth science or an international equivalent with majors in petrology and minerology. The analyst shall have at least three years’ post-graduate professional experience in conducting and reporting on rock petrology. This experience shall include training and experience in the assessment of mineralogy on the performance of aggregates and aggregate mineralogy, used in civil engineering applications.
The procedure shall be as follows:
(a) Identify the rock type by examination of the hand specimen and from sample advice provided. NOTE  If the rock type identification requires the examination of thin sections, the procedures of ASTM C295 would be preferable to this method.
(b) Examine each thin section under the microscope and identify which minerals present are primary and which are secondary. Also identify the presence of veinlets or microcracks in the fabric of the rock and the presence of secondary minerals as linings or infillings within vesicles or primary pores. Record the major compositional and textural features of the section and the distribution of secondary minerals within the fabric of the rock.
(c) Set-up the mechanical stage unit at the starting point of the first traverse line. Determine the point step interval and the traverse line spacing necessary to provide coverage of the whole area of the thin section, within the limit traversed by the mechanical stage. The point step interval and traverse line spacing has to be relevant to the grain size of the rock being examined. A mineral count of at least 600 points along a series of traverses of equal length and spacing is required; that is, the total number of points counted should exceed 600 by at least the number of points attributed to voids (vesicles, microcracks, pores and similar).