Mode

Copper ore from Legnica consists of 17% copper minerals in a quartz (64%) and calcite matrix (19%) (see Figure 4).

**Figure 4.** Copper ore (green sandstone ore): (**a**) hand specimen, (**b**) microphotograph under reflected light.

### Grain Size

The quartz shows a mean grain size of 265 μm and the copper minerals with 277 μm are of similar size. The standard deviation σln of the diameter distribution of the copper minerals shows a scatter parameter of 0.504. Figure 5 shows the grain size distribution of both minerals as identified by QMA.

**Figure 5.** Mineral grain size distribution of the copper ore according to QMA.

### Grain Shape

The shape of the copper minerals of the copper ore is predominantly platy-like. This is confirmed by the values for their elongation E and flatness F (E = 1.224; F = 1.156). In comparison, the shape of the quartz is predominantly needle-like. This is confirmed by respective elongation and flatness values (E = 1.458; F = 1.162).

#### Roughness

The roughness KR of the copper minerals is around 62% and is therefore in a very high range compared to minerals of other rock fabrics.

#### Specific Surface Area

The specific surface area SV of the copper minerals is in the medium range and is around 53 mm2/mm3 per mineral grain. The specific surface area and the roughness characterize the "intergrowth" of the minerals with each other. This intergrowth is an important information since it allows to draw conclusions on the breakage behaviour of a material, the specific energy consumption, wear of comminution machine parts etc.

#### Degree of Clustering

The degree of clustering C shows whether a mineral grain forms an agglomeration in the rock with another mineral grain of the same type. The quartz shows a 6% cluster formation, that is, 6% of all quartz grain surfaces lie next to another quartz grain surface.

#### Space Filling

The very good space filling means that moisture can only adhere to the surface of particles, as there are no pores in the ore sample.
