The weekly democratic statesman. [volume] (Austin, Tex.) 1871-1883, 1881-09-29
snn saha.. Marhle deposits.

Texas rock material for the con-
,truction of massive edifces, be-
comes of great importance at this
lime. 1t has been decided 10 use
none but Texas material i'll the con-
struction of the new capitol; and
it is expected that the state. univer-
sity buildings win also be con-
structed of native stone.
These massive structures will be |
of character vastly different from
anv hitherto constructed OF native |
material. They are destined TO cost |
the people many millions OF dollars;
Too much care cannot be bestowed |
upon the selection OF material; es-
pecially of that which will be eX-
posed TO the winds, rains and frosts
for centuries to come. 1t will be
poor policy, and false economy, to
use defective material, simply be-
cause of its near vicinity to Austin,
or the line of some railroad leading
thereto.
The few wears which have elapsed
since the erection of any building OF
considerable size i'll Texas gives no
reliable time test as to the dura-
bility of material; hence the neces-
sity of every precaution i'll It's selec-
ton. The severest available tests
should be applied, and that which
fails to stand these tests should be
rejected. AS to durability, there is
no test like time, still there are pro-
cesses by which chemicals are made
to do the work of ages. Machinery
is now used to test the strength of
material by determining the exact
amount of pressure which it will
bear.
The chemical composition of rock,
though important to know, offers no
certain indication of hardness or du-
rability. Carbon, in its pure or
crystalized form, is the hardest of
ali known substances, whilst in an
other form, that of graphite, 1T is
one of tie softest. When combined
with lime, it forms the solid marbles
and compact limestones, as well as
the soft chalks. In chemical COM
position the commonest limestone
differs in no respect from the finest
statuary marble. The differ
ence in color, texture, etc,
arises from circumstances con-
| nected with the manner of
| the deposits of the material and the
conditions to which it has been sub
mitted since its formation. 1t has
been proven by actual experiment
| that a block of common limestone
may be converted into beautiful
statuary marble. This may be done
by submitting it TO heat and mOis-
ture under pressure. These power
full agents are capable of etfecting
remarkable changes i'll color and
texture. All fossils will become
completely Obliterated, and the mass
crystalized, and its color changed TO
pure white, should it not contain
| iron or other colOring matter. The
difference between compact lime
stone and true marble, is that the
latter is metamorphic, containing
crystals throughout the mass whilst
the former never having been sub
mitted to heat is non-crystalline i'll
texture. Both were originally form
ed in the same manner by deposit
of calcarious matter under water in
regular strata or layers of greater
or lesser thickness. The kinds which
are Veined, whilst in q semi-sOlid
condition, were by internal forces
broken up into irregular pieces OF
all sizes from that of u grain OF
wheat to cubic foot or more. These
fragments were held in close prox-
unity to each other by the superim-
posed deposits, until again united
by cementing material, often diff.
ferent in color and composition from
the original deposit. These cemen-
ted seams form the veins so much
admired in marbles. Upon the
composition OF this cementing sub
stance depends in great measure
the capability, rs to amount OF
pressure which can be sustained
without crushing.
In some cases the material Of
which the seams are composed is
much more tenacious and durable
than the main substance of the de.
post. In these cases the cementine
substance is not q source of weak
ness but means of strengthening
the mass.
Along the edge of the outcroppins
of the azoic rocks in the south part
of this county there is unmistak'
able evidence of the existence Of
laccolites or subterranean eruptions
: of molten matter from the depths
below. The heat from the
incandescent matter which in
these cases is injected through
dykes to within a few hundred fee
of the surface has metamOrphosed
the limestone beds and converted
them into true marble having g
saccharoidal fracture. In this res
pect the San Saba marble differ:
from the so-called Burnet marble
which is a compact limestone with.
out crystalization. The Burne
marble, whilst in bed, was submitted
to forces which fractured it i'll every
conceivable shape. So completely
was the breaking process carried gu
that it will be impossible to procure
block forming cube of four inch
es but that it will contain more thai
one seam. 1t is unfortunate tina
the fractured surfaces have not beer
cemented together with materia
sufficiently strong to proven
the seams from being opened
with the slightest tap of ;
hammer, or by slight pressure ap
piled to the surface. Some varietie
of the Burnet marble are very hand
some, and had they been submitted
to the metamorphic action to which
the San Saba marbles owe their crys
talline texture they would have beer
very valuable. The name Burne
marble is applied to a class of rock
not only found in Burnet county
but in several adjoining counties.
The San Saba marbles are of man
varieties, but there are in grea
: abundance three kinds. One { tn
most abundanD has II fine rich vel
lowish ground clouded and veinet
with warm colors, pink, purple, or
ange and red. Another, has ligh
fIesh-colored ground, and beautiful
r ly clOuded with light red. A thirt
is white with texture closely re
sembling ivory. Some of thi
last is clouded lightly with green
ish colors. The first mentioned
variety is massive-the bed from
, to IL feet III thickness. 1t can b,
quarried in immense blocks. Th'
second kind is in great abundance
stratified from l to feet in thick
ness. The third, which lies severa
/, miles south of the others, is in strata
, varying in thickness from few
inches to 2 feet. All can be quar-
ried with little expense for strip
ping. For the construction of mas
sive buildings the first variety is ad
mirably adapted. Its crystalline
L torAn..o ociunr IL af ron III and Anrn