1. The groundmass contains interstitial quartz or tridymite or cristobalite.

2. Minerals associated with this include quartz, cristobalite and tridymite, which may all be present in volcanic ash.

3. It can also be produced in the laboratory by compressing cristobalite in a diamond anvil cell to pressures above 40 GPa.

4. Further influence of alkaline solutions decomposes the alunite already precipitated, whereby α-cristobalite remains unchanged or is recrystallized to quartz.

5. Depending on the temperature and on the content of silica and alumina, Aluminosilicate clays, upon heating, form various combinations of alumina, cristobalite, mullite, and liquid

6. Products of natural alteration consisting of cristobalite and alunite could likewise be imitated in experiments, when the trachyandesite was transformed first by alcalic solutions and then by sulphuric acid.