Weekly Arizona journal-miner. [volume] (Prescott, Ariz.) 1903-1908, 1906-03-28

Tissurc vein is n term in common use
among miners and promoters, but not
always with the same meaning. just
at present IN "A number of journals
there * in progress a discussion that
may result ia n more exact use. The
following IL the contribution Of the
Mining and Scientific Press:
Simply described, a fissurc vein is
fracture IN the crust Of the earth,
which has been filled by minerals, in.
filtered into the fracture and dcposi.
ted along its course, either in open cave
like spaces, or in mass of crushed
debris, derived from the a,trition and
crushing Of the vein walls A fissurc
vein presents so many phases as to
render its description in all of it's char
actcristics n somewhat complicated
matter
Many geological text books contain
sketches of " fissurc vcins,' which
show the successive deposition from
the walls toward the center Of minerals
Of various kinds. including silica and
calcitc. with various sulphidcs Of iron,
lead, zine, copper, etc, giving the vein
n comb.like structure, and n banded
appearance. Such veins exist, and in
some mining districts are numerous,
but ordinarily the fissurc vein fails to
show this banded structure, due TO sue.
ccssivc deposits of different kinds Of
minerals
More commonly the vein is bounded
by definite walls. but the vein material
il massive, showing little or no evil
dence of successive deposition, but
rather AN alteration of the crushed
materials derived from the walls by
the movements which have fractured
zone of the country rock within the
limits of the walls and reduced much
of il to fine granular or pulvcrulen'
condition. This crushed rock, being
easily attacked by the waters passing
through the fissurcd zone, Is decom
posed it's soluble portions dissolved out
and the minerals thus removed are re
placed by other Internationally sill
ca (quartz) and one or more Of thu
sulphides of the base metals. with some
times gold or silver, or both. Calcit'
baryta, fluoritc, sidcritc and other min
erals are also occasionally precipitatc'
from these percolating solutions. No
infrequentIy the character of the fiss
urc is distinctly influenced in its strnc
turc by the wall rocks. Thus In I
slaty formation the vein may have
slaty or ribbon structure, and in
massive rock the vein IL more apt 4
assume "A massive structure, or
brccciatcd appearance there being yer.
many pieces of more or less silicific'
rock which are clearly portions of tn
the walls. which have not been finel.
crushed, but which have nevertheless
been altered by the Undertaking solu
tions.
HOW i''ho ''h w w"
altered 10 that they no longer bca
any physical resemblance to the orig
inal rock, can bo readily understood b.
those who have visited gcyscrs an
hot springs in volcanic regions. Their
steam aud sulphurous gases may b
observed issuing from vents In tn
rock, and rocks recently fallen fror
surrounding cliffs within reach Of til
influences Of these vapors and hcatc
waters are found altered to kaolin, q
otherwise changed. II similar water
pass upward through vent in th
car,h's crust--a assure the adjoinin
rocks will he altered in similar maj
ner, and in time the vein minerals wit
which we are familiar will DO dcpo
tied. This is accomplished probabl
by upward moving waters, but in mos
instances whore mining il now bcin
carried on, the process Of vein formi
tion has long since ceased or is on II
wanc, and the water circulation
downward. This downward circui
tion produces other changes in the vel
and we find what is termed secondaI
enrichment. which il 81 beautifully g
pmplihcd IN many copper mines, n