Sierra County advocate. [volume] (Kingston, N.M.) 1884-1960, 1894-04-06
infuence of il. ..eous dy kes of por-
phyry and diorite close by.


| h"uhkbt tukoOub IOCke, QtOtit
the world over seems to be q gres
favorite for gold deposits.
comes up in dykes and intrusiv
sheets, but never in overhows
The color OF the rock at distance
is usually dark greenish grey
II is mainly composed of hor
blened and quartz. and littl
crystals of feldspar. It is tn
weathering Of the horn blend
that gives it its olive green tint
from which it is sometimes called
greenstone. Besides occurring il
dykes and sheets, it sometimes
builds up mountain masses, such
as many of the peculiar cases 0
the Elk mountains.
At times there 10 50 much quart,
and feldspar in the rock, that Itt
light color makes it resem bls
granite, or mora properly syenite
but it's truly eruptive mode Of oc.
currence help 10 distinguish i:
from the latter. In the canons ol
the South Park, Colorado, this
diorite may often be seen RAINING
up through the rocks in narrow
dykes, and spreading out between
the strata in dark greenish grey
beds.
10 New South Wales diorite is
the source of the gold found in the
placers; quartz veins also traverse
this diorite, and pass into the
peighboring schists. In the diorite
they are gold bearing, but not in
the scbists. In other places the
veins are associated with diorits
dykes, and where these do not oc-
cur the veins are barren. At
Victoria the gold veins lie at the
contact of intrusive masses of
diorite and sedimentary rocks,
also IN the metamorphosed silurian
rocks beyond the contact. Pyri-
tons diorites occur gold bearing in
Queensland. In South America
diorite dykes break through Ju
rassic strata, with veins of gold
bearing pyrites. The gold is
found in It's metallic state in com
pound, Of sulphur, arsenic and
iron. The superficial parts of
these veins, appear richer IN, gold
than those of greater depth. The
diorite dykes have altered the ad-
jscent strata and at the point of
alteration or metamorphism occur
the gold-bearing veins coming out
OF the diorite. Diori.s Is the
country rock of the chief gold
veins of Venezuela, and oecxrs In
rotten disintegratlng diorites at
Khutil. Placer gold OF the Urals
is derived from diorite. Also the
gold OF New Guinea, New South
Wales and New Zealand.
sYENITg.
Syenite is another favorite gold
bearing rock. 1t is very like
granite. only that horn klen1e re-
places the mica of the granite. It
is sometimes comparatively light
In color, like light granite, bit
generally it is dark, owing to the
prevalence of horn blende. which
also like in diorits sometimes gives
it an olive grey green cast. Like
granite it occurs in great masses
forming often with granite large
portions of mountain ranges, like
the Wahsatch, Utah. At other
times ii occurs in dykes which
may be eruptivs. In Australia,
dykes of syenite occur crossed by
gold quartz veins, which split up
as they approach the walls of the
dyke, and become rich on entering
the adjacent states.
The Virginia gold belt lies on
slate aud syenite. Gold in queens.
land occurs between granite and
syenite. In the Lion mine
near Prescott, Arizona, free gold
and pyrites occur in broad dykes
OF eyenite, the dykes are full OF
little riyalsts OF quartz, locally
rich in gold.
As syenits is so much like
granite it s probable that many
gold veins said to be in granite,
are more strictly in syenite. The
Mormon Temple is built ont OF
syenite derived from the neighbor-
ing Wahsatck mouatei2so~
GRANITE
This may include massive gran
ite, and granitic rocks, such as
gneiss and schist of the srohoean
age. A large proportion Of our
gold veins 40 well as the gold
found in placsrs. derived from
eranitic rock, are in rocks OF this
kind. Forbes says that the largss.
gold washings Of South America
and probably of the whole world
are derived from this source; veins
have had their origin in granite
and have been injected into sdis-
cent strata Of gneiss and schist.