B.K. Emerson—Dyke of Eleolite-syenite in New Jersey. 307 
The freshest egirite shows six-sided cross-sections (/, 7-2,) 
remarkably regular both in form and cleavage, the latter being 
in straight equidistant lines carried generally clear across the — 
crystal, and thus differing widely from that of augite. It is 
red brown with much depth of fee in cross-sections, blackish 
brown in longitudinal plates, free from enclosures, and without 
trace of fibrous structure. Both in lengthwise and cross 
sections it absorbs the light with a single Nicol’s so aa 
that at the point of extinction it becomes jet black. e pleo- 
chroism is also very marked, ranging from charcoal brown to 
deep emerald green. In other crystals, starting from one end, 
the color in ordinary light changes gradually from dark brown 
into a bright green, and corresponding with this change of 
color the mineral becomes quite suddenly fibrous, and filled 
e 
unchanged portion. The changed portion has all the micro- 
scopic peculiarities of a fibrous hornblende. In longitudinal 
sections of the egirite a cleavage parallel to O appears, ee in 
one instance occurred a well terminated arrow-heade — 
twinning pees 7-7. Its crystals often radiate from or eile a 
cee to mallest pk erst ) ining any clo- 
sures. Besides ‘eae the microlites often radiate from it. 
Beautifully distinct ie occur with the tw weenibe ponies , and 
side of this plane. 
odalite occurs rarely in wholly apolar patches irregularly 
bounded by the other constituents, and showing rude dodeca- 
hedral cleavage. 
The order of crystallization of these minerals is sabarinne ged 
The titanite is plainly the first formed, and had reached its 
limit before the appearance of the other paar rN except 
perhaps the first form (a) of the elxolite. These are almost 
without enclosures of any kind. ext the second portion of 
the elzeolite (4) crystallized out, and during the time of its 
formation the hornblendic mineral, which is included in it in 
scales, as well as the wgirite which radiated from the earlier 
formed titanite, appeared. This green hornblendic mineral as it 
is synchronous with the sgirite and as it is found in the most 
decomposed portion of the eleolite, I. take to be arfvedsonite 
paramorph after the wgirite. 
oward the close of this period the orthoclase, which encloses 
the imperfect crystals of the elxeolite and the wgirite, separated 
out, and all these minerals share the same freedom from micro- 
lites, a great swarm of which is included in the third form of 
