The Geology and Petrography of Crater Lake National Park, 1902
PART II.
HYPERSTHENE-DACITES.
MINERAL COMPONENTS.
OTHER MINERALS.
Olivine was observed only in the older secretions that accompany these dacites and will be referred to under that head. Apatite and zircon occur as occasional inclosures in the different phenocrysts, as does also magnetite. The first of these, however, is not easily found. Its color is sometimes a distinct brown, and the form roundish prismatic.
The order of crystallization for the above minerals, leaving out these last-named accessory minerals is as follows: Hypersthene, plagioclase. augite, and hornblende, with some variability as to the plagioclase, as this mineral is at times older than hypersthene.
