Abrasion and wearing resistance of a rock aggregate are essential factors for utilisa- tion in road construction purposes. These two properties are measured by two tests, Los Angeles (LA)- and Micro-Deval (MD)-test methods. This study uses a large database of samples of crystalline rocks collected from the Sveconorvegian Bamble sector, within the new highway E18 Tvedestrand - Arendal. Fieldwork, petrography of the selected samples, and supplementary scanning electron microscope (SEM) characterisation have been used to determine the significance of regional geology, mineral compositions, fracture densities, microstructures and alteration processes to the resulting LA- and MD-values. Influence of the Oslo rifting phase has been reported in Kragerø, northeast of the study area. The presented results reveal that samples collected near Tvedestrand, the northernmost part of the studied region, present a trend of higher, disapproved LA-values, implying that the rifting phase has affected the Bamble sector southwest of Kragerø, and lead to the lower abrasion resistance of the rocks. Petrography and SEM analyses in a range of samples reveal several alteration processes, e.g., resulting in the development of micropores. These features seem to lead to lower abrasion resistance, and samples containing micropores have higher LA-values. Other mi- crostructures such as high microfracture densities and fractured foliations also affect LA-values negatively. The Oslo rift does not, on the other hand, appear to influence the MD-values. Micro- pores resulting from the above mentioned processes have not negatively influenced the MD-test results. The low MD-values for the samples containing micropores are interpreted to result from the polishing of the rock aggregates during the MD- testing. As rock aggregates get less angular, the micropores are partially removed from the rock surface, thus reducing the negative influence on the wearing abrasion. The only factor that has been found to have a negative impact on the MD-values is high microfracture density.