3.2.1. QMA Results (Granodiorite)

#### Mode

Granodiorite from Kindisch consists of 34% quartz, 48% feldspar and 18% mica (see Figure 9).

**Figure 9.** Granodiorite (**a**) hand specimen, (**b**) microphotograph under transmitted light with lambda/4 plate.

The effects of these minerals on the mechanical characteristics of the rock and, hence, its comminution behaviour and abrasivity are quite different. The mineral quartz is a positive development in terms of strength, weathering and temperature resistance. Due to its high Mohs hardness, it increases the abrasivity of a rock in comminution. The feldspars consist of polysynthetic twinned plagioclase and alkali feldspars. The most singular property of mica is its physical structure. As a sheet mineral it can be split into strong, flexible films having good high-temperature resistance. Its mechanical properties, however, vary substantially depending on the direction of loads relative to the direction of the films. While the grain strength is rather high with compression loads rectangular to the film planes the material strength with regard to compression loads acting in the planes is usually comparably low.

#### Grain Size

The mean grain size of all minerals is rather different. The quartz shows a mean grain size of 732 μm, the feldspar 928 μm, the mica 647 μm. The overall mean grain size of the rock is 810 μm (Figure 10). The diameter distribution of the mica shows a scatter parameter of 0.414.

**Figure 10.** Mineral grain size distribution of granodiorite.

#### Grain Shape

The grain shape of the mica looks like needle-shaped. This is confirmed by the values of their elongation and flatness (E = 1.968; F = 1.059). In comparison, the overall grain shape of all minerals of granodiorite is mainly needle-platy, with elongation and flatness values (E = 1.425; F = 1.221).

#### Roughness

The roughness KR of the mica minerals is approximately 38% and is therefore in very high range compared to minerals of other rock fabrics.

#### Specific Surface Area

The specific surface area SV of the mica minerals is approximately 11 mm2/mm3 per mineral grain.

#### Degree of Clustering

The mica shows a 13% cluster formation, which means 13% of all quartz grain surfaces lie next to another mica grain surface.

#### Isotropic Orientation

The isotropic orientation degree Kis is about 79%. These values give an indication that the production of cubic products is only possible by increased machine expenditures (e.g., multi-stage comminution and preferably by impact loading) and matched operating mode of the processing plant (e.g., high stress intensity).

3.2.2. CT Results (Granodiorite)
