Semi-weekly standard. [volume] (Raleigh, N.C.) 1853-18??, 1863-06-12

For the standard.
No.2.-Clay, its Origin, Composition, Uses, etc.
BY E. EHMoNs, STATE GEoLoGIsT.
Kaolin, or as it is sometimes called china clay,
and sometimes also petuRtre is derived directly
from the felSpar of granite granite compounds
We may learn how this happens by reference to
the composition Of felSpar: thus, the pureSt form
of this mineral consists of slick, $685. alumine,
1877; lime, :1.34 potash, 1899; soda, l.Ol.-
Water charged with carbonc acid seems to be first
absorbed and the result of decomposition is an hy-
dros siLicate c GtuaninG or silica 10 afumina A,
wafkrl5; the original felspar is anhydrOus, des-
ttute Of water Part of the silica, set free, is
moved in combination with potash.
1t is worthy of remark here, that combinations
in the act of breaking up arr free to form new
bodies; they possess in the instant of breaking up
power to act upon and combine with the bodies in
contact; they are said then to be in that case in
nascent state; one in which their combination
givesa new birth to bodies. If the nascent state is
passed and the new birth is unconsummated, the
force power of combination is lost Thus, we
may undertake to force union of silica with alum
ina by forciOle contact by attrtion in MORTAR the
result is only simple mixture In the decompo-
stion of felspar several minerals may also be form
ed crystals of quartz or the more beautiful gem,
opal, by combining with the proper proportion Of
water.
Kaolin is white in state of purity; it coheres
only slightly and is destitute in part Of the pastic
and its beds are generally known chalk beds
Being derived from granite, it is in immediate
nection with the parent rock, and for the reason
that granite region is more or less elevated we
must look for Kaolin only among the granite hills
of district 1t is distributed in this State in this
way: The search for porcelain clay in the lower
Eastern district would be unsuccessful; but west
of Raleigh 1t would be in its geological position,
and wherever granite and its allied compounds &C.
cur, may probably be found.
Kaolin derives its importance from its infusibility
cor its persistence unchanged in the intensest heat
of the furnace, and when mixed with more fusibie
bodies than ITSELF becomes by its semi
translucent body, still remaining a pure white,
grayiSh or milk white In England the ffnest clay
for porcelain china in Cornwall where it is
obtained by running stream Of water over the de-
composing beds of granite which carries with it the
finer and purer particles of the clay, and is finally
received into ponds tanks where it is allowed to
subSide. The fine sediment is removed, and after
being exposed to the atmosphere or months, is
ready for use. This clay, when it has been dried
at the temperature of 2l2 deg. Fab, consists Of
Slick 1882
Alumne, 1874
Prot oxide of iron, 027
Lime 036
Magnesia, GA
Water 1857
The foregoing will serve for comparison with the
North Carolina KaolIns 1t is not however, to be
inferred that the best clays of this class possess
uniform or fixed composition.
The most celebrated Kaon of France is found at
Limoges, and consists of slick, AZ OF; alumlne, a.
IS; water 1917, with traces Of lime, magnesa and
potash 1t is plain however, that as clay is pro-
duct of decomposition, its constitution depends
much upon the state of change which it has under
gone especially with respect to lime, magnesia and
potash for these bodies ultimately disappear from
the mass produced.
The beds of Kaolin of North Carolina are nu-
merous, and give US foundation to hope that they
Will become important in the manufacture of fine
pottery ware. The finest kinds occur in Macon
jackson, Buncombe, Catawba and Chatham coun-
ties-the coarser in Wake and on the western Dor
der Of Johnston county.
The Jackson and Macon county Kaolins are snow
white, frable, or fall to powder readily, but form
with water a semplastc mass, which, on drying is
tender easily broken. Heated to bright redness
in the furnace, it is still white, and when raised to
an intense white heat is still infused and white
These experiments with all the cays were careful
ly executed by my Assistant, E. sEmnons, Jr., to-
gether with many other trials to test their value
for crucibles and friedrich. The Jackson clay is
composed of slick 40, alumine 800, water II !; |
iron, lime and magnesa, none, or mere traces. The
Kaoln of Buncombe county is composed of slick
$50, alumine 800, water 100; that of Chatham
county, slick $50, alumne 80. water no. lime,
iron and magnesia, none The latter dissolves and
gelatinzes in muriatic acid 1t is white, compact
and infusible and in ne is the most perfect Kaolin
we have yet seem On comparison with the Corn
wall and French clays it will be that they close
ly resemble them and each other in their compost
ton. 1t may be safely inferred therefore, that
they are equally we'll adapted to the manufacture of
the finest porcelain seeing that their behavior when
subjected to heat confirms the inference wo have
made.