The Wilmingtonian., 1886-07-24
MINERALS AND ROCKS OF
NORTHERN DELAWARE.

Comparatively speaking little is known of
the geology and mineralogy Of the extreme
northern part of Delaware. The formations in
the Hundreds Of Christiana, Brandywine,
Mill Creek and portion of White Clay
Creek, belong to the class of rocks called
primary, consisting Of the common blue rock
or gneiss, and sometimes of the trap and
granite. There are also small formations
of limestone and serpentine. Very few min
erals are found in Delaware in connection
with the gneiss rock.
The serpentine shows only, SO far as is
known, in three localities. The first is the
outcrop which appears on the road between
Greenville and Mt Cuba, Christiana Hundred
The road has been cut through the vein, but
SO long ago that a fresh exposure had to be
made. The serpentine varies in color from
a light apple green to dark olive ,and
sometimes showing dark lead blue shade.
1t is scanned much with magnesia, which
makes it an exceedingly beautiful stone when
polished. BY digging down below the
weather worn rock several veins of asbestos
are found. Most of it is in that puculiar
state-asbesL:-form serpentiLe The two min
erals seem to be mingled together. Both
have changed until they now exhibit a sub
stance which is neither one nor the other.
The veins of this asbestos in Chrstiana
Hundred occur between two faces of serpen-
tine, and are from one half an inch to three
in width A short distance from the serpen-
tine vein there is an opening of granitic vein
in the shape of feldspar quarry 1t is a
curiously old place. The quarry is now no.
thing more than a pit, half filed with water,
and lies near the road in one corner of
field. Great masses of moss-covered rock
are strewn about, and the rank weeds and
green grass almost cover the small piles of
debris. The small tool house belonging to
the Quarrying Company, weather beaten and
decayed stands near by. Everything shown
neglect. The place has been abandoned for
years, the supply Of commercial Geldspar hav-
ing been exhausted. 1t is however, yet in
teresting to the mineralogist. Small speci-
mems of the very fine translucent variety of
feldspar may be found by little hard work
with the hammer. That dark green mineral
apatite was at one time abundant, but
scarcely trace of it can now be seen. The
very rare variety of garnet called cinnamon
stone, which mostly comes from India, was
also one of the minerals of this vein, but
now in common with many others is not to
be found here A peculiar variety of mica is
abundant, 1t is that form known as plum
Z use mtca II resembles cone radIating
from its centre Examined closely APPETIZER
study cannot be found. A variety of YER
mlculite is here in iarge quantities. 1t be-
longs to the mica family, but very different
in colcr. 1t exfolates-opens fan shape
when heat is applied to the edge of thin
section The writer has, in experimenting,
with it succeeded in producing a very good
bronze powder of several shades.
About mile further on the same road,
iron has been found. Immense veins of as
bestos underlie the earth for several acres.
Here also is another out-crop of the same
vein of serpentine. Chrmoe ofa good quality
has been taken from this spot. On Dixon's
farm granitc vein has been open for many
years, and large quantities of pure white field
spar have been taken out, but the supply is
now exhausted. The vein of granite is quite
large and appears to cross that of the ser
pentiuo. Large masses of white quartz lit
about in several fields, near this locality
Some of them have faint rose OF pink tint
Brandywine Hundred contains several in
terestng points. The principal feldspal
opening is on Mr.. liamsay's farm. Aninfer
: ior common sort Of stone cOmpOses this vein
This quarry shows.the grandual change o.
feldspar into kaolin, from the hard rocl
through the different stages of decomposition
q to the soft clay, Almost the only minera
e at this point is species of mica which i
similar to that found iu Penusbury few
e miles above in Pennsylvania. The mica con
}. tanning reticulated magnetic non is distlibut
| ed through it in such a..manuel that the thinn
est possible slice will contain delicate tracing
4 of IRON. thin section seen under the mi
i croscope is magnificent sight The write
q has perceived immense trees, fallen trunk
v and beautiful hair-like ferns. BeautiGr
u masses of color which cannot be seen by th
b naked eye, ale shown. The writer has ais
r seen crystals of seaGoal shapes and sizes son
It not the one hundreth of an inch in size. Tn
a. mica assumes several forms. One is Ion
70 and narrow and it would seem as il they ha
rs been under an immense knife which had CT
t. their edges as perfectly as it would qu
of paper. Others are Of au irregular form
\, gradually taperiug to point, pyramid lik
n sometimes resembling a silver spider