# Hydrothermal Manufacture of Zeolitic Lightweight Aggregates from Clay and Marine Plastic Litter
## 3 Results and Discussion
### Zeolitic Lightweight Aggregates Obtained from Kaolin and Different Proportions of Marine Plastic
#### 3.2.1 Mineralogical Changes and Zeolitization
Therefore, the addition of the rejected Mg-clay does not seem to have inhibited the crystallization of cancriine (and to a certain extent neither of zeolite A), but it did so for the rest of the phases mentioned above. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multirow{2}{*}{**Kao**} & \multirow{2}{*}{**III**} & \multirow{2}{*}{**Sm**} & \multirow{2}{*}{**Sp**} & \multirow{2}{*}{**Q**} & \multirow{2}{*}{**Plag**} & \multirow{2}{*}{**Fp**} & \multirow{2}{*}{**Cal**} & \multirow{2}{*}{**Dol**} & \multirow{2}{*}{**Pig**} & \multirow{2}{*}{**Mu**} & \multirow{2}{*}{**Zeo**} & \multirow{2}{*}{**Can**} & \multirow{2}{*}{**Sod**} & \multirow{2}{*}{**Phi**} & \multirow{2}{*}{**Am**} & \(\Sigma\) & **Other** \\  & & & & & & & & & & & & & & & **line** & **line** \\ \hline Kaolin & & & & & & & & & & & & & & & & & \\ (unfired) & & & & & & & & & & & & & & & & & \\ \hline Rejected & & & & & & & & & & & & & & & & & \\ Mg-clay & & & & & & & & & & & & & & & & & \\ (unfired) & & & & & & & & & & & & & & & & & \\ \hline SOK-10-900 & & & & & & & & & & & & & & & & & & \\ \({}^{\circ}\) & & & & & & & & & & & & & & & & & \\ \hline SiK2-10P-900 & & & & & & & & & & & & & & & & & & \\ \({}^{\circ}\) & & & & & & & & & & & & & & & & & \\ \hline SiK2-10P-900 & & & & & & & & & & & & & & & & & & \\ \({}^{\circ}\) & & & & & & & & & & & & & & & & & \\ \hline SiK2-10P-900 & & & & & & & & & & & & & & & & & & \\ \({}^{\circ}\) & & & & & & & & & & & & & & & & & \\ \hline \hline \end{tabular}  
* Kao = kaolinite; Ill = illite; Sm = smectite; Sp = sepiolite; Q = quartz; Plag = plagioclase; Fp = alkali feldspar; Cal = calcite; DoI = dolomite; Pig = pig pigione; Mu = mulite; Zeo A = zeolite A; Can = cancriine; Sod = sodalite; Phi = phillipsite; Neph = nepheline; Am = amorphous phase. \({}^{\circ}\) Minerals registered as zeolites in the database of the International Zeolite Association [28]. \({}^{\circ}\) Feldspatiud with zeolitic framework type [28]. \({}^{\circ}\) The naming of the samples follows the same rule as that in Table 3, but in this case the proportion of rejected Mg-clay versus kaolin is distinguished with the term S for the former, which refers to its high content of smectite and sepiolite. Therefore, S0K1 indicates a 0:1 ratio (i.e., 100% kaolin) and Si:K2 a 1:2 ratio (33% rejected Mg-clay and 67% kaolin).  
\end{table} 
Table 4: Mineralogical composition of the kaolin, the rejected Mg-clay and the lightweight aggregates obtained at 900 \({}^{\circ}\)C from kaolin and its mixture 1:2 with rejected Mg-clay (term S because of its high content in smectite and sepiolite) and 10 wt.% MPF (10P). Letter H = material hydrothermally treated after firing. The habit of the crystals presents parallels with several of those indicated previously in Figure 5. According to the SEM images in Figure 7, in many areas the only elongated crystals that can be observed are flattened, typical of nepheline (Figure 7), which contrasts with the fact that cancinrite is the dominant mineral in the two zeolitized samples (Table 4). This should be because cancinrite aggregates can also take other morphologies, such as the rounded ones [31] shown in Figure 7. Regarding nepheline crystals, some Y-shaped crystal associations have been observed (Figure 7b), something that also appears in the study of [PERSON] et al. [30]. This type of structure is actually formed by the epitaxial growth of a butterfly twin, typical of nepheline [29], on another crystal of the same mineral.