These volcanics lack cordierite or garnet. The spots are darker, containing cordierite and biotite. Characteristic minerals include andalusite, biotite and cordierite. It was confused with a similar mineral cordierite because of their similar coloring. Catalytic converters are commonly made from ceramics containing a large proportion of synthetic cordierite. Examples of peraluminous minerals include biotite, muscovite, cordierite, andalusite and garnet. These minerals include cordierite, muscovite, garnet, and sillimanite. These volcanics contain chloritised cordierite and some have garnet. The melt reaction produces a granitic melt and solid orthopyroxene and cordierite. These volcanics contain chloritised cordierite, and some have garnet. These volcanics contain chloritised cordierite and some have red almandine garnet. For example, andalusite could be associated with cordierite but never with hypersthene. Cordierite typically occurs in contact or regional metamorphism of pelitic rocks. Within S-type volcanics, cordierite occurs in place of clinopyroxene. Cordierite is structurally similar to beryl, and is a common metamorphic mineral.