1. Iron rich olivine is a relatively common constituent of acidic and alkaline igneous rocks such as volcanic obsidians, rhyolites, trachytes and phonolites and plutonic quartz syenites where it is associated with amphiboles.

2. The main characteristics for the sialic origin of the Aeolean magmas are: excess of Als2O3; the presence of minerals of evidently not magmatic origin (cordierite, garnet, andalusite and sillimanite); inclusions of relicts of metamorphic schists besides granites and granodiorites; the fact, that some of these magmas are characterized by superheating (e. g. the obsidians of Lipari-island).