The Wallace miner. [volume] (Wallace, Idaho) 1907-current, 1913-09-25

into a blue. regularly banded non -cs.l :
careous shale. This in turn 10 oyerlain
lby comparatively small thickness Of
green rocks very similar TO those at
the base Of the formation.
The blue shaie forming the major
part Of the upper member presents re-
markable variations in thickness. In
the basin Of the ST. Joe river. to the
south Of the area here described. II Is
apparently not less than 5000 feet
thick, hut near Striped peak, south
vest OF Wallace. It's thickness is insig-
nificant. The thinning Of these beds
has not been continuously traced and
its cause is still obscure.
The lower member Of the formation
also il of very uneven thickness, be-
ing apparently much thicker near Sal
tese than near Mullan. although the
structure Is not understood with suffi
cient thoroughness to permit rellab't
photographic measurements. The to-
tai thickness OF the Newland formation
| in the middle part Of the Occur
Id'Alcne district, where the upper mem
Der is almost unr presented, was es.
tlmated as 1000 feet. but this Is cer-
tainly less than the combined thick
ness Of the lower and middle members
near Saltese.
Striped Peak Formation.
The striped peak formation occupies
only small part of the area mapped
| It consists of shales and sandstones
with shallow water markings and Is
! remarkably similar to the st. Regis
formation, The prevailing color Is i
greenish gray. but some. beds are pur-
lple
luneous Rocks.
Diabase--The largest mass of dia-
base In he region is the Wishards sill
a sheet 400 or 500 feet In maximum
thickness, which is intercalated In ths
middle member Of the Newland forna.
ton 1t persists at the same strait
graphic horizon for remarkable dis.
sance having been traced from the
read Of Placer creek southeastward Il
| St. Joe river. 80 miles away TIL,
constancy of its photographic posi-
ion proves that it was intruded be-
lore the Algonkian rocks were defcrm-
ed, and 1t has been folded and faultet
with them. 1t Is Of great use in de-
ciphering structure, because 1t is more
readily followed than any stratum d
the sedimentary series, being general.
| Y conspicuous for it's dark tone, boli
,utcrops and the scantiness Of the veg
citation growing on It,
| The rock has the normal appearapst
of diabase, Its general color is BLACK
to dark gray with a tinge of green; its
texture Is coarse to fine. The miner.
ais visible to the naked eye are whi-t
feldspar, dull greenish-black augil,
Ind amphibole and black iron ore u
metallic luster The feldspar forms
crystals that give many narrow OBJ
ong sections. No Divine is visible
even under the miscroscope, which re
,eals considerable amounts of quartz
llkali feldspar and biotite.
The shay rocks Of the Newland for
nation are distinctly metamorphose'
by this largest diabase intrusion, blu
he metamorphism is limited to a dis
,ance of a few yards across the bed
lding.
This diabasc also forms some thin
ner, inconspicuous stills in the New
land formation, one Of which, near tn
boundary between the middle and tn
lower divisions, was seen in severa
places south of Saltese. Diabase dixie
have not been found in the area MOI
especially considered here, although
here Is one on the south side Of War,
peak, penetrating rocks that underli
he Newland formation.
Other lntrusives.-No other igneou
rocks than the diabase form large ,
conspicuous masses and none az
shown on the geologic map.
In the vicinity of Mullan there ar
numerous bikes OF rocks that wer
classified In the report on the Coeu
fAlene district as lamprophyres. Sup
critically these resemble the fine
grained portion Of the diabase in be
| ng dark and Of crystalline texture
| out they are heedle-like crystals 0
black hornblende and their feldspa
does not show well defined outlines
Biotite is somewhat conspicuous i
most specimens.
Several of these bikes are crossed b
he Hunter tunnel. One or two other
.rop out in the vicinity Of the Gettys
burg prospect, and one is cut by tn
workings of the Morning mine, On
n two are penetrated by the working
If the Star prospect, west of the Nor
aing. In this same prospect are tw
Or three bikes of greenish- gray por
pbyry. which are possibly offshoot
rom the monzonite intrusion expose
near Gem. about miles to the north
west, but the rocks are too badly de
composed to supply conclusive petro
graphic evidence of such a relation.
A thin sill Of decomposed basic ig
ieous rock resembling diabase Is in
circulated in the St Regis formatio
IN Willow creek and penetrated. by tn
Carney Copper prospect.