**8. Applications (slatenorm and slatecalculation)**

Slatenorm (later slatecalculation) was originally developed as a method of determining the mineral content to assess the suitability of the rock as a roofing slate. For this purpose, more than 360 analyses were carried out similar to [20] based on practical experience in normal, oxidizing, occasional oxidizing and carbonate slate, and also in high carbon content-slate with carbonate and hard slate divided. There are also shale and phyllite/schist. For reasons of clarity, not all types in [9] are to be treated.

Additional results will be added in ref. [33]. The nine samples of the group "oxidizing slates" are actually only errors in the selection during the extraction or manufacture of "occasional oxidizing slates" (17 samples). As far as all other properties are concerned, it is a normal slate (see **Figure 2**). The 94 samples of the group "high carbon content- slates" are also normal slates, but with a no carbonate carbon content of over 1%. EN 12326 [36] excludes roofing slate with a content of more than 2%.

Cardenes et al. [26] summarized the cleavage and perforability of roofing slate in a diagram of rigid (= standard minerals: qz + an + ab + or = Quartz and Feldspar) and elastic minerals (= standard minerals: mu + pa + ill + br + mac + mc + fac + fc = Mica, Hydro-mica and Chlorite). However, the classes "soft," "medium hard," "hard," and

**Figure 2.** *Diagram showing the ratio of rigid to elastic minerals, calculated with slatecalculation, with changes according to [26].*

"very hard" listed there are imprecise. The reasons for these properties are not always related to the rigid mineral content and especially the quartz content. The determination of the quartz content remains an important prerequisite for the evaluation of a roofing slate deposit.

The class boundaries in **Figure 2** (gray lines) provided in ref. [26] should be corrected. Some slates with carbonate that can be processed normally fall into the wrong class there (there is medium-hard). Obviously, the good cleavability of the carbonates or, to a lesser extent, the feldspars or chloritoids have to be included in the assessment. This leads to new class boundaries in **Figure 2** (black lines). There is a narrow field between the classes "normal" and "hard" in which slates of both classes occur. In **Figure 2**, some slates from the groups' carbonate slate, high carbon content-slate, phyllite/schist, and shale have been assigned the properties hard or normal.

The phyllosilicates calculated in slatecalculation (after [9]) show a total mica content from usually above 40% (up to a maximum of 60%) and a chlorite content from more than 10% (up to a maximum of 25%) in normal slates (**Figure 3**). Only for samples with higher carbonate ("carbonate" and "with carbonate") or higher carbon ("high carbon content"), are the proportions lower. The ratio of mica (mu + pa + ill + br) to chlorite (mac + mc + fac + fc) is 3 to 1. In "normal" slates, the Fe-chlorites content (fac + fc) outweighs the Mg-chlorites content (mac + mc). The calculated proportion of hydro-micas (ill and br) could reflect (in addition to the Kübler index or the organic matter reflectance [37, 38], **Figure 4**) the degree of metamorphism in most of the samples.

That is why, phyllites always have hydro-mica values of 0% in the calculation outputs.

The slates of the Iberian Variscides also show very low positive percentages of hydro-micas, while slates from the Central European Variscides (Ardennes and Rhenohercynian zone) have a lower metamorphic grade and show higher values of hydro-micas (**Figures 3** and **4**).

*Normative Mineralogy Especially for Shales, Slates, and Phyllites DOI: http://dx.doi.org/10.5772/intechopen.102346*

**Figure 3.** *Phyllosilicates as calculated by slatecalculation: Types of phyllosilicates (after [9]).*

**Figure 4.**

*Methods for determining the grade of metamorphosis (according to [9, 33, 38, 39]).*

## **9. Discussion**

Correspondences between the standard methods for sediments (SEDNORM, SEDMIN, PELNORM, subsection 4) on the one hand and slatenorm and slatecalculation, on the other hand, are to be expected. As **Tables 5** and **6** shows, however, these are low. There are rather clear differences.




**Table 5.**

*Comparison of the results from slatenorm, slatecalculation and SEDMIN. \* = TiO2 (kaolinite) = 0, \*\* = TiO2 (kaolinite) = 1.1. Empty fields = not calculated.*

In **Table 5**, the five examples from **Table 3** are calculated using the specified methods. **Table 6** contains the standard mineral results of two further examples in **Table 3** from the literature given there. Standard minerals remain, which are not calculated and are marked as gaps in **Tables 5** and **6**. In SEDNORM, SEDMIN, and PELNORM, the clay minerals kaolinite (2SiO2 Al2O3 0.05TiO2 2H2O, Mol. Wt of mineral: 262.15, according to ref. [6]) and smectite (4SiO2 Al2O3 0.1Na2O 0.1CaO 10.9 H2O: 550.46 of mineral: 550.46 of mineral, according to ref. [6]). In contrast to the other methods, a distinction is made in slatenorm and slatecalculation between Na and K mica or Na and K hydro-mica. In the other methods, on the other hand, only K mica


### **Table 6.**

*Comparison of standard calculation results taken from the literature (SEDNORM [5] and PELNORM [7]) with own calculations according to SEDMIN [6], slatenorm, and slatecalculation. M = modal mineral inventory, N = calculated [7], \* = 6, 7 in Table 6 in [5]. Analyzed from Table 3.*

(muskovite) or illite is calculated. PELNORM [7] only considers a small proportion of Na2O in the formula for illite (0.025Na2O 0.30K2O Al2O3 0.2MgO 0.125Fe2O3 3.40SiO2 Mol. Wt of mineral: 374.17). SEDMIN uses the very low TiO2 content in the above chemical formula (only 0.05 in 2SiO2 Al2O3 0.05TiO2 2H2O!) to calculate kaolinite. This leads to high kaolinite contents in phyllites and slates, where this mineral is not even present (**Table 5**).

As mentioned in ref. [9], the Abakabili shale (**Table 5**) may contain a small amount of clay minerals. In the literature [40], the main component is illite with 30–38%, smectite/montmorillonite with 20–30%, quartz with 28–30% (instead of 11% in **Table 5**), and kaolinite with only 15–25% (instead of 55% in **Table 5**).

There are often TiO2 minerals such as rutile (TiO2), ilmenite (FeO TiO2 or titanomagnetite FeO Fe2O3 TiO2) in the group of slates, which in slatenorm and slatecalculation are consequently calculated as standard minerals ru, ilm, and/or tm. Using the TiO2 in the SEDMIN standard calculation of kaolinite leads to the excessively high results in **Table 5**. For this reason, a corrected value of TiO2 (if used to calculate kaolinite: \* = 0 \*\* = 1.1) was used there as an alternative.

SEDNORM and SEDMIN specify the Fe compounds to a large extent as hematite (Fe2O3). However, this mineral is rarely found in shales and slates. Slatenorm and slatecalculation, therefore, count Fe above all to be monovalent Fe sulfides. Hematite is only calculated if, in rare cases, the color of the rock is red and not black or green (see **Figure 1** in [9]). In **Table 6**, the mean value of the worldwide sedimentary rocks is given from the chemical analysis in **Table 3** (after [5, 34]). With SEDNORM, only calculation results are given for which, according to standard mineral calculations, there are no longer any excess MgO, Na2O, K2O, or CO2 (6, 7 in **Table 6** in [5]). As far as the quartz, the carbonates and the sum of the phyllosilicates are concerned, the methods slatenorm, slatecalculation, SEDMIN, and SEDNORM show sufficient agreement.
