176 The American Geolo,s:ist. September, looi. 
This rock is composed largely of hypersthene with only a little 
feldspar. It is a common type and is intermediate between the noryte 
and pyroxenyte. 
PLATE XVIII. 
Fig. I. — Peridotyte (zvehrlyte). 
From near the point where the west branch of Stone run crosses 
the state line. Section No. 43. Magnified 20 diameters. Ordinary 
light. The olivine is partially altered to serpentine. The diallage 
exhibits its characteristic columnar structure and its black inclusions. 
The olivine is confined chiefly to certain bonds or layers, one of which 
shows on the side of the figure. This mineral also occurs included in 
the diallage. 
Fig. 2. — Pyroxenyte (Iiyperstlienytc). 
From Oakwood. Section No. 159. Magnified 20 diameters. 
Nicols partially crossed (made 55° angle with crossed position). 
This rock is composed entirely of hypersthene. Eight or ten dif- 
ferent individuals are shown in the figure. 
PLATE XIX. 
Fig. I. — Saiissiirite gabbro. 
From Octoraro creek just below the state line. Section No. 120. 
Magnified 30 diameters. Ordinary light. 
This rock is a typical saussurite gabbro composed of fibrous, green, 
secondary hornblende (smaragdite), and white, opaque saussurite. 
The latter is made up almost entirely of zoisite. One good sized 
columnar crystal of this mineral is shown, bordered on either side 
by smaller individuals of the same. 
Fig. 2. — Quartz-diorytc with epidotized feldspar. 
From one-quarter of a mile below Porter Bridge on Octoraro 
creek. Section No. 266. Magnified 30 diameters. Ordinary light. 
The feldspar is replaced by aggregates composed of minute crystals 
of epidote. The dark, granular patches which appear scattered through 
the clear white quartz, and which mark the outlines of the feldspar 
crystals, are epidote. Several hornblende individuals show on the 
edge of the field. 
