Note 63 — Chapter IX · DESCRIPTION OF THE GEOLOGICAL AND GENERAL PHYSICAL FEATURES (continued)

It is referred to the 5th sub-order (genus 18) of the hypersthene-augite-andesites characterised by prismatic pyroxene and more or less parallel felspar lathes in the groundmass, as described on p. 289. It displays abundant opaque porphyritic plagioclase giving extinctions of oligoclase-andesine. The pyroxene phenocrysts have dark alteration-borders. There is a little altered interstitial glass. Spec. grav. 2·55.