abstract:The feldspathoids are a group of tectosilicate minerals which resemble feldspars but have a different structure and much lower silica content. They occur in rare and unusual types of igneous rocks.
The notesdescribethe common mineralssuch asquartzandits polymorphs, coesite, tridymite and cristobalite, feldspar, plagioclase, feldspathoids, pyroxenes, amphiboles, etc.