The daily crescent. [volume] ([New Orleans, La.]) 1848-1851, 1849-02-08

their search.
Almost all the varieties of mica exhibit with the
aid of good magnfyng glass, remarkable ap-
pearance, distinguishing this metal from gold by the
simple view. Well-defned lines of dark color
are seen, separated by intervals which, looked at
sideways, of an ridiscent appearance, the green
and occasionally the red predominating. Gold, on
the contrary, exhibits mass OF fine yellow, more
or less brilliant, which are never traversed by the
light. Mica heated TO redness becomes opaque,
and assumes light yellow color; under the blow
pipe it produces an enamel gray, or inclined to
green; gold under the blow-p pipe does not change.
There is great variety of mcas but, to facilitate
their study, they may be divided into three princi
pal varieties: The aluninous, whose lusre is Wire
Gus these (such as the rose coOred and greensh
micas of the United States and of Mexico, are not
acted on by sulphuric acid. Micas of an uncertain
lustre, such the yellowsh and black are readily
acted on by boiling in sulphuric acid. The micas
lepidohes are of diversified coors, violaceous, red
dish, greenishyellow. They combine so many
properties that it is very difficult to give general
summary respecting them.
The following enter most commonly into their
composition; but very many exceptions to this will
be found in the analysis of particular parcels Sill
ca, oxide of iron, potassa, oxide of manganese and
magnesia also the existence of fuoric acid of
small quantities Of oxide of titanium has been
proved.
OfMe Distincttue Characteristics Of Ndtiue Gold.
Native gold is of pure lustrous yellow; without
ordor taste Ii is bent with facility provided it be
not of too great thickness. Heated with the blow
pipe it melts and communicates no color to the
fuxes with which it has been mixed being smelted
it remains in state of fxity and preserves so long
as it is maintained in fluid state clear blueish
green color, but cooling it resumes its character
stic yellow color.
The ustre of gold is greater than that of copper,
tin and lead less than that of patna, iron and
silver.
1t is not as hard as iron, patina, copper and sill
yer; but harder than lead or tim
1t can be cut with knife.
1t is fused more easily than copper, iron and pla-
tina; less easily than mercury, tin, lead and silver
Pure nitric, sulphuric and hydrochloric acids do
not separately act upon 1t. The choro-ntric
acid, the nlenstrum reglum of the old chemists,
acts readily it at gentle heat and dissoves it.
The choro-ntric acid to dissolve gold, is COM
posed of one part Of pure nitric acid and at $50 of
Beaume areometer and of two parts of pure hydro
clorin acid at 22o of the same areometer.
Precipitated from solution in the nlenstrum re-
GUM by water of Ammonia, the gold collects at the
bottom of the vessel in yellow foccutent mass !;
collected on filter and well washed, it forms full
minating god which on exposure TO heat detonates
with force.
If it be detonated on different metals, different
results are obtained. On tin, lead, anthony, bis
muth, arsenic, trace is left of a reddish yellow
which passes into brown. On silver, "copper" iron,
cobalt, zinc, its appearance is of metallic state.
Gold melted by the action of the fire suffers hardly
any waste but exposed to the rays of the sun i'll
the focus of lens, ii becomes covered with a
vreous pelcle of purple color and is volat-
LIKED.
The electric spark gives violet colored cover
ing to gold. Pure gold may be rendered soft
as lead, by throwing it when melted great many
times into liquid preparation of ammonia and
alcohol
Of Minerals containing Gold
Il al. e.
of spanges in aluvial soils, in the beds of rivers
1t is present also, but more rarely, in grains or
humps of variable size, which have occasionally
been known to attain the weight of seven to eight
pounds. These are called pepites Gold is also
found in amorphous masses in the beds of torrents
at one, two OF three feet below the surface of the
ground. The earths which contain gold are either
sandy or argillaceous indifferenty; they vary in
color very frequently they ferruginous, of a
yellow black color. In general, auriferous lands
are dry and sterile. The most ordinary localities
of gold are argilaceous schist mixed with porphy-
rrized clay, accompanied with quartz galena and
iron pyrites These auriierous lands form extended
plains. 1t has been long supposed that the rivers
which carry gold take their sources IN aurferous
mountains. But all the researches undertaken to
ascertain the truth Of this superstition have been
fruilless. 1t is observed that gold is always found
in larger quantity in the entering angles OF streams
and rivers. Storms and heavy rains, by carrying
away the sands which are lighter, frequently ex-
hibit the gold to view
Gold found in spangles in alluvium is separated
from the earth with which it is mixed mechanically
by washing. The different processes are very SIM
pie, but they insufficient to the entire separation
of the metal without certain previous preparations
The other auriferous minerals worked In the
Mexican Cordilleras may be divided into three
classes.
!. Gold disseminated in milky quartz, gneiss,
micaceous schist; adhering either to sulphate of
barytes or carbonate of lime.
2. Gold disseminated in iron pyrites, in which il
is absolutely imperceptible.
3. Gold disseminated in the hydroxides of iron
accruing from the decomposition of these substances
In the metallic veins in the first class, gold is
found in mixing with silver, copper, iron. arsenic
aniimony, tin and telurium occasion ally it is met
with in the native state under the form Of branches
of fine threads bent on themselves even regu-
larry crystalized in cubes or octohedrons. Gold is
extracted from these mines by picking, bocarding
and washing. The auriferous sui phureis and arse
nurets are first roasted they then smelted in
bars, which are again roasted. They are smeited
again-this time with lead-and an auriferous lead
is obtained, which is refined by copellation. The
other minerals, if little rich, are at once smelted
with lead, without roasting or preliminary smelling,
and then copelled.
Gold in the second class of minerals can only be
obtained by amalgamation. Every one engaged IN
the study of mining must have heard OF the cele-
brated Mexican method for the extraction of gold
and silver by amalgamation. The Mexican miners
are the most expert in the world in this kind of
practice, and / render them this justice much
the more willingly, as am indebted to them for
the practical knowledge | possess of this process.
II may readily be conceived that in an article for a
daily Journal, could not enter upon the subject of
the management of gold mines, as the most essen
tia details of the operation would force me into a
long and minute investigation. II, hereafter, |
should continue this article, and should enter upon
the consideration of argentierous minerals, whose
habitats and varieties are much more numerous
than those of the auriferous, shall then endeavor
to enter into some metallurgic details. | should
then also occupy myself with the comparison of
the different methods of refining and the systems of
mnting used by the Americans, Mexicans and
French. In the meanwhile, | will say that in the
laboratories of assays of the minis, since 1888, the
process of Gay Lussac (voie humidel has been
adopted-an excellent process, when the title of the
silver is known to some thousandths nearly, and
which is only mixed with copper. The operation
then pyes a correct standard Rut in the majority