Weekly standard. [volume] (Raleigh, N.C.) 1858-1865, 1863-06-10
clays,. their Origin, CenPesitlon and Uses.
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Clay, in the noeaclatare Of geoldgists, is arock,
houeh soft and destitute of some Of the most str-
ting physical which rocks are sup.
,osed to possess. As rocks, however, their origin
las been subsequent to all those masses which are
'tricty primary or formed anterior to organic be-
ngs. Clays aFe then secondary in respect to their
origin, beiag derived invariably from preexbting
materials. They are produced by the influences OF
forces acting upon solid masses g
granite, gnsiss and smicS @snd taicose states. Of
these forces @sbonic acid ind water arc an6ng the
most energetia Bodies, however, which are CON-
pex II their composition are unstable, and it seems
As if their elements were struggling to break up
their old Combinations and form new compounds |
more. simple and stable in their arrangements.-
Thus We find many GRANTEES undergoing radical
changes being resolved ultimately into clAy, sand
and oxides Of the metals These are stable bodies,
being neutral in all their relations to the ordinary
forces of nature. Water acts chemically and me-
In the former capacity it dmsol+es q
large number of bodies; in The latter it breaks up
in freezing the most cohesive rocks, and ultimately
reduces them to powder. 1t thus prepares the way
for the joint chemical action of itself and carbonic
acid. In these arrangements we cannot fail to re-
eognze the most important provision sor the sus-
tenaace of the vegetable and animal kingdoms.
The clays considered geologieaaly, may belongto
the most ancient the more recent formations md
it is only by investigating their relations to other
rocks or by their organic remains that their relative
ages can be determined Clays are still forming by
the influence of'the forces we have already referred
to. Kaolins, 50 much esteemed for porcelain, are
forming to-day from the. coarse GRANTEES of our
mountain chains Clay is usually found in beds;
the most important exception occurs in the cays Of
vein assures or the lodes of metals. 1t is the
auccan of miners These beds are commonly found
in depressions of the earth's surface, in valleys
where they are exposed to view on the banks of
rivers and creeks But certain kinds of clay belong
to mountainous districts as the Kso)in already re-
ferred to. Although granite and other allied COM
pounds are prolific source of clay, yet there are
many others. Chemists have shown that alumine
is one of the most common elements in the mine
raj kingdom. All rocks except the pure sandstones
and. limestone, contain alumine, and by far the
greater proportion of the earthly minerals contain
alumne as essential constituent; it is therefore,
of the most widely diffused bodies in the min.
eral kingdom. But alumins ana clay not iden-
tical bodies. Alumine is the pure oxide Of the
metal aluminium. If it is wished to know what
this. pure body il, make solution Of one part of
alum in SIX parts of boiling water, and then add
solution Of carbonate of potash or comnaon pearl
ASH. A white bulky preeipitate is separated; this
is alumna or alumine. of chemists It is not, how
ever, properly clay; it is the basis of clay. When
it combines With sile1 it becomes clay, and its
properties are totally changed Alumne is light,
doculent body, scarcely plastic or susceptible of
being moulded but in combination with slick, body
equally destitute Of Elasticity it becomes in the
highest sense plastic and rnouldable. 1t takes any
shape under the hand Of the potter, and being en-
trely unelastc retains the most delicate impression
or figure which may be inscribed upon it.
The beds of clay which have been referred to, are
not strictly beds Of alumina but in the teehhinal
language ofrehemists, are silieates Of alumina.-
The best idea We can get of silex, is that in the
mass Of fine quartz crystal. Under favorable con-
dtions, this substance combines with alumine and
forms variety Of clay. In addition, however, te
this chemical union of slick and alumine, there is
usually mixture of silex in the condition of sand
which is variable quantity. This additional mix
ture of sand modi6es, as we shall see, the proper
ties Of clays, and fit them for greater variety
purposes. Pure a.umine is rare in nature, and j,
known in the sapphire and ruby gems which ranl
next in hardness and xalss 4osths dis0eodL
Clays are frequently impure, from the presenct
| of iron, which may be known by its red or yellow
| ish color, or by combination with carbonates o.
| lime and msgnesia, the presence of which may be
| known by their efervescing with ACIDS. These
bodies also modify the properties of clay, and may
spoil it for fine pottery, they may not be at all
detrimental to it when employed for other purposes
1t is difficult to give satisfactory classification o!
elays. "A distinguished French chemist Classics
them under the terms freproef tusi6le calcareous,
and Jsrruginous;; names which indicate, in part,
certain properties as we'll as certain combinations.
The origin of clay may serve as basis for CLASH
ication Thus the GRANTEES give origin to all the
Kaolins, while the states furnish directly the plastic,
pipe clays and probably fullers earths. 1t is true,
the slate clays may have been derived originally
from the GRANTEES and their allied compounds, for
slate bing sedimentary rock, mzy have been also
derived from these older rocks. For practical
purposes the division Of clay into 1usi5e and ints
SIDE is the most important division: But should
remark the terms are relative; by nfusible is really
meant great difficulty in FUSION not an impossibility,
for by the instrumenta.y Of the proper heat which
may be dexterously applied, all bodies are fusible.
Having made he'foregoing preliminary remarks,
shall proceed in the next communication to speak
of the composition and localities of the Kaons Of
! North Carolina. =. :.