1894. ] NEW YORK ACADEMY OF SCIENCES. 217 
weathering, with rounded grains of monoclinic pyroxene and 
plagioclase, and containing some hornblende, magnetite, tita- 
nite, pyrite, calcite or a little quartz. In fresh exposures the 
plagioclase is seen to be finely twinned and is often accompanied 
by dark, red or pink garnet. The rock is usually dark colored, 
fine grained and decomposes readily. It shows all stages, how- 
ever, up to coarsely crystalline aggregates of highly lustrous 
and readily cleavable masses of labradorite with large imbedded 
augite crystals often several inches across, the labradorite show- 
ing excellent striz on the basal section, and with a micro-per- 
Fic. I. KELYPHITE RIM SURROUNDING GARNET. THE GARNET CoN- 
TAINS Micro-CRYSTALS. 
thitie interpenetration. Norite may be said to occur only 
rarely, if it all. In spite of the prevalent use of the term in 
previous writings on the region, microscopic examination re- 
veals hypersthene in small amounts in a few sections, probably 
resulting, however, from some variation in the usual gabbro. 
The anorthosite types are light colored and consist almost 
purely of plagioclase, with little or no augite or hypersthene, 
and no macroscopic accessories. Alteration of the contained 
lnagnetite to leucoxene, and of the plagioclase to a milky kaolin 
is observable in many rock sections; secondary rosettes of the 
