Mohave County miner., 1894-05-12
cA<micai Theories about Formation q
Nuggets.


thai nuggets sre often found very lar
.vsy IRON any parent vein or reef. Their
ANAL size offering little surface for the
ussssuie Of water, combined with their
sreat weight, would hardly allow water
10 carry them to such distance, Al d in
favor OF the chemical theory. Gold in
plscers 10 sometimes found In iron py-
rites assuming the form Of rootlets, and
replacing coaly matter, implying chem.
icAl action and solution, and that goli
existed in ordinary waters, and deposited
uith pyriie. Gold, II is maintained. IL
contained in mineral waters permeating
roks and placers, influencing the pre-
cipita,ion oi gold, which conrrc,es around
certain substances congenial to IL. such
~ other loose grains Of gold, cubes OF
pyrite, etc.
Gold In solution has this tendency, for
chloride Of gold Was decomposed by a
piece Of cork failing accidentally into tho
solution, and was precipitated around y
small piece OF metallic gold that hap.
pencil TO be present, greatly increasing
Ito size Similarly il has been found to
concrete around cube Of pyri,es. Gold
crystals sometimes contain iron ore OF
iron pyri,ss as nucleus." From this
Il appears that organic matter will de-
compose q solution Of gold and precipi-
tate it around some nucleus offered 10 IL.
As to the TACT that placer gold is gen.
orally purer than vein gold. this, too. is
favor OF the chemical theory. as it is
found that gold may he greatly puride'l
Of its alloy by dissolvirg and reprecipi.
tsting it.
Nuggets may be formed and PARTICLES
Of gold may increase in sire, through de-
posit Of gold from waters percolsting
through the placer. And ss at the time
Of volcanic eruptioos, such as were pre-.
vAlent at the time OF the placer for
nation, ~ shown by the lava Gaping
Of the deep placers Of Caliiornis. these
waters we're both hot alkaline and So
line, and therefore especially favorable
10 carrying gold in solution. Gold exists
in some saline waters and has been lie
tecied in sea water. in the latter case
probably derived from the rocks Cold
700 Was found in solution in the water OF
anime in New Zealand.
Again, the pebbles OF congiomeraies
sre at times found cemenied with iron
ore, containing gold, implying solution.
and that the gold salt was in the same
solution that deposited the pyri'es. Gold
has great affinity for silver or quartz.
Gold probably came into the gold vein in
. solution Of quartz Of silver, the latter
derived from the elements composing the
adj AGENT rock, such AS mica, hornhlende
and feldspzr. Gold probably exists in
minute form in there little minerals.
All native suIphides, such as copper
and iron pyrites are liable to contain both
silver AMI gold. In the imposition
Of q vein charged with snch metals. sil.
yer may be oxidized away in solution,
whist the gold will be carried of in q
very minute state. Gold being ailoyed
with silver, and silver With gold. shows
that at the time VI !O, 'nposition, the
separation Was incomplete.
In illustration OF some Of these chemi-
cal changes going on in placers, Is the
occurrence Of gold ia the deep lava-cap-
ped pIacers Of California. These placers
are the gravel drifts Of ancient river beds,
covered up by lava flows 100 to 200 feet
thick. The placers are worked by tun.
nels driven beneath the lava. Waters
percolating through these lava Il Iws aud
reaching the grsvels below. are charged
with alkali from the alkaline minerals
composing the lava. These alkaline
waters are also charged with silver from
other elements OF the lava. Hence the
driitwood OF these ancient river beds has
been silicifisd by these silicifying waters.
The gravels are also cemenied by silica.
These waters contained iron siso and de.
posted iron pyrites around the fossil
wood. The gold may have been in so
luton in iron sulphste or else along with
the iron in alkaline suiphde.
Whilst the wood decayed it was par
TALLY replaced by quartz and partly by
iron pyrites, the latter produced nv dc
oxidation Of iron sulphate by the wooiy
organic matter. In this pyrite gold IL
found, sometimes in rounded grains and