Lynchburg daily Virginian. [volume] (Lynchburg [Va.]) 1852-1861, 1854-02-03
AGRICULTURAL GEOLOGY
BY JOSIAH lIOLBROOK.
10. N.-GRANlrE FORMATIONS.

No. N.-GRANITE FORMATIONS.
Mica is II compound of oxides, more compound
ed than either quartz or telspar. 1t contains all
the oxides entering into both these minerals, with
the addition oi manganese much used Tor bleach
ing salts, (cloride Of lime.) Mica also contains
traces of the silieute of magncsia-the article
used in the manufacture ofepsom salts and other
chemicals. This silicnte, M its name denotes,
contains slick, or the oxide of silicum. 1t has
been found by the progress of geology in large
quantities, both in Pennsylvania and Maryland.
From il have been made various chemicals, aud
among them EPSON salts, (~sulphate of magnesia,)
at 50 cheap a rate, in such quantities, as entire
ly to supersede the importation of this article, so
extensively used for medical purposes. In con
ncction with this silicate and other magnetism
minerals, chrome ore (ehl Ornate Of irony has been
found, and chrome yellow (chromatc of lcad) made
from it, with such success rs to reduce the
price Of thnt valuable paint from fifteen dollars
to twenty-five cents n pound thus bringing the
benefit of geology and chemistry 70 every midi
vidual in the communicate least to every man
and woman who rides in n carriage with yellow
paint, aud to every child who uses an atlas with
colorcd maps.
Mica is not an important clement in soils, and
in rocks is less ahundm: than either quartz or
%fclspar. Though not abundant in rocks, it is one
of the three materials of granite, and has am i'm
portant influence in modifying the character OF
rocks in fitting them both for agricultural and ar
chltcctural purpose 1t gives TO gnciss and mi
ca slate, both granite formations, a facility in be-
ing worked into slabs of great extended surface,
fitting them for sidewalks, bridges, fl, ors, farm
enclosures, and numerous other purposes. These
two abundant rocks in granite formations can be
readily formed into slabs of an extended and
smooth surface, by the use of the hammer. chisel,
and wedge while most rocks, not containing mi
ca, require the drill in addition to the instruments
named.
Good specimens of mica slate may be seen in
the walks from the National Capitol leading to
Pennsylvania and Maryland avenues. 1t is OBJ
tanned from Bolton, Connecticut, twelve miles
east of Hartford. Gneiss is the common mate.
rial used for sidewalks in Washington, as it is
for the Easements of all the public buildings now
in progress in the national metropolis. 1t is OBJ
tanned from the banks of the Potomac. from five
to eight miles above Washington. In this ex-
h~austlcss and valuable deposit, are interspersed
extensively very brilliant cubical crystals of the
sulphuret-not sulphate-ofiron, known among
the miners as fools goid,' and strikingly illus
trates the old adage that ''all is not gold that gilt
tcrs.i
ExPERIMEST.-Any person drawing "A piece of
felspar across some quartz, and then the quartz
across the telspar, may ascertain which scratches
the other, and of course the comparative hard
ness of these two essential elements of soils, the
oldest friends and the strongest 'unionists' upon
our globe.