Sierra County advocate. [volume] (Kingston, N.M.) 1884-1960, 1894-04-06

Gold, he says, is a normal constit-
uent OF the granite itself, aud
though it would not pay to grind
down whole mountains of granite,
yet where locally granite 10 decom-
posed for several hundred feet in
I depth, it sometimes repsys the la
Dor OF washing the whole mass for
the sake OF che gold in it. From
the granite also are veins injected
into overlying Silurian or Cambrian
strata.
The nuggety reef of Victoria 10
in granite. The veins themselves
are only coarser and more quart
zose variety OF granite containing
more quartz and lass mica than the
granite commonly called pigmatitic
VEINS. AT Beresof. Russia, gold
quartz veins appear in dykes of
fine-grained granite. Granite is
the country rock of the gold veius
Of Canada, and OF Gilpin county,
Colorado, and many other gold
bearing regions of the world might
be cited. Nor is it to be wondered
at this is the great parent of gold,
seeing that it forms the axis of
nearly all our great mountain
ranges. The eands in rivers
throughout the world carrying
more or less gold are for the
greater part derived from commin-
uted granite.
PoRPHYRY. $780,
This rock of which there are
endless shades and varieties, is
char acterlzed by the distinctness
with which crystals OF quartz or
feldspsr are set in it's ground mass,
like plums in a pudding, giving it
strongly spotted appearance.
This rock ia invariably OF eriptiye
and igneous origin, belonging to
the class, however, Of plutonic
eruptiont, which have never poured
out like modern lavas over the sur
face but have come up in dykes
and intruded thick sheets into the
adjacent strata Its mode OF occur
renee is like diorite. and gold oc-
ours IN it's decomposed dykes and
sheets III a similar manner. We
have mentioned already the Anti
och mine OF Leadvills in a quartz
porphyry dyke, other gold mines
are similarly located in that region
in Colorado, often without any
quartz or quartz veins, simply q
rotten dyke more or less impreg
pated with free gold, and in its
deeper, harder parts with gold
bearing pyrites.
The Bolerra gold veins In United
States OF Colombia are in metal.
liferous porphyry. 60 several OF
the geld mines of Idaho Territory
and Montana, notably the De-
Lamar mine. In Queensland the
gold bearing drift of the Cape
river gold field is all from feldsite
porphyry, and Is derived, not from
quartz veins in the porpbyry, but
from the porphyry itself, and fel-
site porphyry is the bedrock on
which the placers lie. In one
place a porphyritic dyke was dis
covered. aud whenever IL crossed
The sl.tes the drift gold was rich.
Porphyritic dykes are the
source of alluvial gold 10 Borneo.
In the Leadvills region the Cal
ifornia and other great gold placers
are derived from the breaking up
OF vast masses of gold bearing
porphyries in the Mosquito rAIge,
some OF which have lately been
worked for gold st Leadville.
sERPESTrNE.
This 10 green magnesisn rock
found amongst eruptive
rocks, but sometimes also among
This rock sometimes
produces gold. Thus In Australia
at one locality the bed rock is
silurian shaies with cliffs OF ssrpsn.
tine crossed by dyke of porphyry. |
Near this dyke the reck was very |
rich in gold as far as the schist |
and serpentine extended and |
at the junction of the
sehist. and sArpeutines. Some Of
the Queensland reefs are serpen-
tipeus, also Newfoundland and
MoRs RECENT ERUPTIvH ROCKS.
naId ooonra in q 0raat nanv