The Wallace miner. [volume] (Wallace, Idaho) 1907-current, 1916-10-05

The terml contact deposits" should
be restricted 10 deposits which have
been formed by igneous metamor-
phism and which carry the mineral
of such action. Such
use eliminates from this category
many forms of deposit that have been
so termed simply because they hap
pen TO occur between rocks of two
different kinds. Contact deposits, as
thus defined occur mostly in lime
stone at or near its contact with an
intrusive igneous rock. They are very
irregular in form. internationally
they differ from other deposits by the
formation of oxides
md sulphides, principally OF iron, and
BY the association or these oxides and
'ulphides with silicate minerals.
Segregated Vein.
The term segregated vein" has
some times been used to define ma
erials that have been concentrated in
| sedimentary bed. AS a general rule
however, the name of a process should
lot be used as the definition of type
u deposit, and segregation" is more
appropriately applied to the gathering
ogether of material in a molten mag
ma In either sense reference to
deposit as Segregated does not suf-
iciently characterize it as a type.
Impreenation.
The term "impregnation" has been
lsed by different writer's in many ana
senses. 1t properly signi-
les the Introduction of mineral sub
tances in finely disseminated con-
ition into rocks, either as a filing of
pen spaces or as a replacement of
ertain minerals. To describe ore oc-
urring in small, irregular, discon-
ected particles throughout the mass
/ rock, disseminated deposits" is Il
ignification.
Metasomatism.
Metas1omatism may be defined as
he process by which, through chemi-
al interchange, a mineral or an ag-
regate of mineral undergoes partial
l complete change in chemical con-
titution The term 'metasomatism"
J of wider application than pseudo
for the process it desig
ates does not necessarily involve the
reservation of the crystalline form of
he original mineral. 1t may or may
OF be accompanied by a change in
olume.
Replacement.
AS a general term synonymous with
replacement is pre-
=rable to substitution, which is a
hemical term strictly defined as "the
gplacing of one or more elements or
ldicles in a compound by other ele-
rents or compounds" restricted
sage to which replacement is not
onhned. Replacement may be either
artial or complete, according as only
par VI lllS WI lOlC VI OllC loNN VI
mineral has been replaced by another.
Alteration.
The term alteration applies to the
artial change of substance in a rock
r mineral which does not neces-
arily involve it's replacement by ano-
her. The process is purely chemical.
Decomposition.
The term decomposition signifies
he decay of a rock or mineral into
econdary products, usually accom-
,anied by disintegration, so that it in
olives a physical as we'll as a chemi
al change and is most commonly
Effected by weathering.
Weathering.
The term 'weathering' should be
confined to changes in cohesion and
of rocks near the sur
ace by the decomposing and oxidizing
elton of surface waters, by variations
n temperature, and by other atmos-
here and surface agencies The tend
ncy Of such changes is to destroy the
ock as a geologic unit
Enrichment.
In many sulphide deposits the valu-
BILE metals haze been concentrated by
olutions that have descended from
he zone of oxidation. AS commonly
sed, the expression Secondary en-
although having some justi-
cation as an elliptic phrase, is taut-
logic in form and should be avoided.
he idea which this term is intended
D convey may be expressed by en-
ichment," secondary segregation,
downward enrichment or supergene
nrichment,' according to choice or
Mining Terms.
In describing a mine it is well to
tate concisely the extent and char
cter of the mine openings, for which
he terms in general use, given in the
blowing paragraphs, should be en-
loyed. If local term, not in gene
al use, is employed its meaning
houdl be stated.
hiatt, Incline, Slope, Winze, Raise,
Chute, Slope.
The term shaft if not qualified,
leans vertical opening starting at
he surface. shaft that follows the
nclination of vein or bed that is
ot vertical is called an inclined shaft,
+ simply an incline. In coal mines
uch an incline is commonly termed a