A black or brown mineral that is an iron-rich form of olivine and occurs in many igneous rocks.
- ‘Several pools of syenitic magma were separated from the main body of the melt, each eventually being emplaced as quartz syenite, fayalite granite, and riebeckite granite.’
- ‘Associated with the fayalite are quartz, amphibole, and magnetite.’
- ‘These minerals occur with manganoan fayalite and manganoan magnetite in a single sample.’
Mid 19th century: from Fayal (the name of an island in the Azores) + -ite.