Der äquivalente Quarzgehalt – Historischer Rückblick und seine Zukunft in der Anwendung der Abrasivitätsprognose.

The assessment of the abrasion resistance of minerals and their influence is an important aspect in engineering geology and rock mechanics. Questions with regard to rock excavation and the expected wear parameters play a decisive role. Various test methods have been developed over the decades to assess the hardness properties and abrasiveness of minerals and rocks. These include direct tests on rock samples, hardness tests but also parameters derived from mineralogical and petrographic data, such as the equivalent quartz content (FEQu). The values used today for determining the FEQu exist since more than 100 years, and are named after August Rosiwal (1860–1923), the pioneer in the field of grinding tests, referred to as Rosiwal factors. The present work deals with this approach, compiles the factors of various authors, and establishes correlations with other hardness parameters. Using laboratory data, the FEQu are calculated and compared amongst the different sources. It is also shown how the FEQu can be directly related to the widely used CERCHAR test, on the basis of CAI values of selected reference minerals. The FEQu cannot record structural influences, but quartz as a common reference in the CERCHAR test and FEQu offers the possibility of directly linking the two parameters.