Bisbee daily review., 1908-08-12

rocks NAV furnish solutions contain
ing. or capable of precipitating, met,
|als; or various minerals or organic
matter may be present IN these rocks,
which may also yield, or. directly or
indirectly, cause the deposition OF
ores. so that even slight changes In
their composition may determine the
value, or character, of an ore deposit.
Many instances could be cited showing
the influence of differences In the
country rock, and one richment will
not be out of place for many rich
zones are due to this cause. The hts
tory of an ore deposit may be, and
often has been, very complex; a par
tial segregation may have occurred
during the cooling of an igneous rock,
later there may have been further
concentration through the agency OF
ascending solutions, and subsequently.
descending waters may have leached
out the upper portions of veins and
have deposited the material lower
down on contact vita sulphides, or
other minerals. thus forming an en-
riehed zone. Many factors govern the
depth of this zone, and, in some cases.
lit may be found at, or near, the sur
/ face. owing to the removal of over
lying material by erosion, resulting
eventually in rich oxidized minerals
above the ground water. then possibly
a belt of rich sulphides, followed by
: lean sulphurets below. In many in
stances the upper portions OF veins
I have been enriched by the addition Of
mineral derived from those parts of
the veins longsince carried away. De
seending waters may carry the more
44,9 80 fh n
ers, which are less soluble or more
readily precipitated, so that a gold or
silver mine may with depth become
! a copper mine, or lead may give place
/ to zinc: minerals may also be -depos-
tied in a more or less definite order
! from ascending solutions depending
upon many circumstances, and when
upward and downward moving solu-
lions meet. containing, as they may,
very different substances, precipitation
7 of some of their contents is very
likely to occur. Silver, in the form
of chloride, is usually more abundant
! in the silver mines of arid regions
/ than in those of other localities, and
I in these dry districts there is also a
| tendency towards the accumulation of
soluble alkajies and alkaline chloTides,
which. in couItries of heavier rainfall
are carried away to the sea; "Alkali
/ Ike with reason is often pictured in
saloon, for he is a product OF dry
and thirsty land where the scanty wa
tiers may be unfit to drink, loaded, as
they frequently are, with salts of va
| rious kinds, and these soluble chic
rides, and descending solutions con-
ttaining them are undoubtedly often
responsible for the relative abund-
ance of silver chloride in silver mines
| in desert countries. When the rich
mess of an ore body bears a relation
to the surface or to the level of the
ground water it is reasonable to sup
pose that in many cases the concen-
ltratiOn has been largely brought
about by descending waters.
| In brief it appears that many ore
deposits, instead of resulting from
single concentration have been
worked over time and time again.
Sometimes after the formation Of a
imineTal-bearing vein, later move
ngcnts, or iDtrusiOns OF molten rock,
nsay causs fractures and give rise TO
solutions which may enrich the vein
in particular localities, or may intro
duce minerals not before present, in
7 either instances resulting in erratic
/ naturalization. These solutions may
! carry their contents a long distance,
Tor precipitation may take place, in
the case of an igneous intrusion, upon
its borders or in fractures subsequent
lily formed while cooling in the rock
itself The sarinkage during soidifi-
cation may also result in more or less
continuous openings between the once
molten rock and the adjacent forma-
ton, and here ores are frequently
found. The distance to which com
pounds may travel in solution depends
upon many factors, among them be-
ling the kinds and amounts present.
1.-THE character of the fractures. the
lpresence or absence of materials ca
lpable OF precipitating them, the tenn
lperature and the pressure.
In making minerals artifcially it
has been found that small quantities
Iof certain substances greatly facili-
|, ltate capitalization, and they may
have played a part in the deposition
. lsOme ores; among such compounds
Iare algaline fiuOrides, borates, tung
states, phosphates, chlorides, and last
but not least, water under pressure
Tine attraction of like TO like may
sometimes account for punches OF
: mineral, for once a solution has com
Z lmenced to deposit a substance, its
presence in solid form is apt to at
) ttract more of the same kind. Colo
, nuggets occasionally show concen
! itric structure which in these cases
would carefully Indicate some sucf
: Iorigin, and the growth of crystals O
: Ian kinds is undoubtedly influenced b.
5 this law, which, in its application Il
), the ANIMAL kingdom, was long sinc'
+ recognized, as evidenced by the OLD
: Iproverb, Birds of a feather flock to
d lgether.''
n Irregular naturalization may resul
n | from other factors than those indicat
e led, but the possible causes already
e outlined probably apply to the maj
s lority of cases; two things can be sal
( lin their favor, they are founded upol
e Icommon sense, and the influence, a
s Iieast of some of them, has been dem
4 Ionstrated by observation In man.
e instances it may be a matter of grea
Idiffiieulty to account fer rich or
: shoots and punches, for, in the natur
5 lof things. the evidence must be cir
!. icuElstantial and structural, or othe
: features, dominant az tae time, ma.
. later have been 10 great extent OF
liberated. On the other hand. careful
: Istudy may reveal side fractures
s faults. folds, swellings, pinches, dii
/, ifereDees IN wall rocks and various
s conditions already referred TO.
e On the genesis OF ore deposits tn
Hast WORD may never be said, the sui
! iject- as a whole. differing greatly Il
1 THAT respect from this particular al
/. iffcIe Suffice IL 10 say in closing tina