Basic Rocks of Northeastern Maryland. — Leonard. 151 
4. Olivine-noryte. 
5. Saussurite noryte. 
The first named, made up almost wholly of hypersthene and 
bytownite, is by far the most common type, the other varieties 
being- of rare occurrence. 
The porphyritic facies was found near the Mount Hope 
church and consisted of a rather fine-grained groundmass in 
which were imbedded large phenocrysts of diallage. 
The specimens of quartz-noryte were collected from a 
boulder near the junction of Stone run and Octoraro creek. It 
resembles very closely the quartz-noryte found at Mount Hope, 
near Baltimore, and described by U. S. Grant.* The quartz 
appears in limpid, colorless, or light blue grains, sometimes 
wnth a diameter of one-eighth of an inch (3 millimeters). It is 
filled with slender, hair-like needles, probably of rutile, though 
this could not be definitely determined. This quartz has 
every appearance of being an original constituent and not a 
product of replacement or infiltration. 
The almost entire absence of quartz from the pyroxene 
rocks of this area is noteworthy. It has already been shown 
to be an important constituent in the closely associated diorytes. 
Moreover, the gabbros near Wilmington, Delaware, not more 
than twenty-five miles to the east, are known to contain an 
abundance of quartz. But in this region the gabbros and 
norytes only rarely carry any free silica. 
A typical noryte (IV) from one mile west of the Oak 
Grove schoolhouse was analyzed by Mr. W. G. Hillebrand of 
the U. S. Geological Survey, with the following- results. The 
rock is very fresh and composed of bytownite and hypersthene 
with some accessory magnetite. 
IV. 
Si02 48.02 MnO 18 
Ti02 23 CaO 11.42 
Zr02 none SrO none 
AI2O3 20.01 BaO none 
V2O3 02(019) MgO 10.05 
CroOa 03(027) K20.". 05 
Fe203 1.13t NaoO 51 
FeO 7.29t UO2 trace 
NiO. CoO 01 H2O below 105° C... .10 
♦Johns Hopkins University Circulars, Xo. ]0.3. Feb., 1893. 
tSubject to correction for influence of possible pyrrhotite. 
