BULLETIN OF THE LABORATORIES 
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ite is also present in abundance in short, irregular crystals, some of 
which is uralitic, showing alteration to hornblende, and contains inclu- 
sions of magnetite grains. Some of the augite grains are polysomatic. 
Olivine is also scattered through the section showing brownish altera- 
tion along margin and cleavage lines. Magnetite and apatite are also 
present together with a few grains or scales of hematite. No garnets 
were found in this section. Dialage is doubtfuly determined. The 
rock is a typical Olivine Diabase. 
The next sample studied was obtained near this trap and is of a 
coarser granular structure and lighter colored. Large crystals of 
quartz and plagioclase are scattered through it. In section the same 
displays a field, the greater portion of which is hornblende in short 
irregular crystals, forming the main mass of the rock. Through this 
are scattered crystals of orthorhombic augite, enstatite, apparently an 
alteration product of the hornblende. The plagioclase is in small lath- 
shaped crystals of labradorite and together with quartz, forms a small 
portion of base. A few crystals of magnetite and apatite are present 
with a few scales of hematite as an alteration product of magnetite. 
Another rock sample taken from near the contact line, is of a finer 
crystalline structure having cooled more rapidly from a state of fluid- 
ity. It is dark gray in color with reddish brown spots containing gar- 
nets scattered throughout ; . *one exposed edge giving indications of 
weathering. In section we find hornblende in short irregular crystals 
forming nearly one-half the mass with labradorite feldspar in abun- 
dance, and interpenetration quite noticable as indicating secondary 
origin. They also contain cavities of air or glass. Garnets in some 
cases occupy a great part of the field ; they are of a salmon red color 
and contain inclusions of magnetite dust and fluidal cavitites. Near 
these is found quartz and feldspar and a little magnetite in regular sec- 
tions. These two last rocks mentioned are Diorites and are thought 
from the position and structure to be products of the action of the dia- 
bases upon the metamorphic rock through which the diabase has forced 
its way to the surface. The gneisses and schists, according to the 
geological map of that state, lie unconformably upon the underlying 
rock and have probably a sedimentary origin. The diorites seem not 
to be simply diabase altered to diorite, as maintained by Mr. Wads- 
worth, but are perfectly fresh and it rather seems that these rocks are 
paragenetic and the formation of diorite is accounted for by contact 
with the diabase, which by means of its heat fused the surrounding 
