9. Genus of the Augite-Andesites
Formula.—Aug, matr, non-flu, oph, phen, vitr.
Characters.—The felspar-lathes and prisms of the groundmass are not in flow-arrangement. The augite of the groundmass is ophitic or semi-ophitic. Glassy plagioclase phenocrysts.
This genus may be divided into two sub-genera,
- (a) Porphyritic, where the average size of the plagioclase phenocrysts
- is 3 mm. and over.
- (b) Non-porphyritic, where the size is less than 3 mm.