AS 1141.26:2019

The objective of this Method is to provide a microscopic procedure for determining the percentage of secondary minerals, including deuteric minerals, present in igneous rocks.

This Method sets out the method for determining the content of secondary or deuteric minerals of rock spalls, bore cores and aggregates of igneous rocks using a petrological microscope.
This Method is not applicable to rocks that have developed a clearly identifiable metamorphic texture or mineral assemblage, or to sedimentary rocks.
NOTE 1 As secondary minerals are not necessarily deleterious, the method should not be used alone to provide a measure of the quality of the source rock or product.
NOTE 2 The method is suitable for continuing routine assessment of known rock sources as confirmation that the extent and type of secondary minerals have not changed significantly and do not exceed accepted specification limits.
This Method should not be used —
(a) to investigate new rock sources or for previously unknown rock types in known sources;
(b) to investigate other properties of rocks which may limit engineering applications (e.g. potential alkali aggregate reactivity or respirable silica content);
(c) to investigate failures; or
(d) when the genesis of the rock is unclear (e.g. is a deep seated rock type considered a melt or a high grade metamorphic).
In all these cases a more detailed petrological method is recommended.
NOTE 3 Throughout most of Australia the procedure of ASTM C-295 is usually employed.

First published as AS 1141.26-1996.
Second edition 2008.
Third edition 2019.