Note 79 — Chapter XII · DESCRIPTION OF THE GEOLOGICAL AND GENERAL PHYSICAL FEATURES (continued)
Reading edition
They are blackish and somewhat compact (sp. gr. 2·67-2·71) and have very small felspar-lathes less than ·1 mm. long. They contain both rhombic and monoclinic pyroxene, and are referred to genera 1 and 13 of the hypersthene-augite-andesites.