Montana oil and mining journal. [volume] (Great Falls, Mont.) 1931-1953, 1936-04-25

OF ore IS the process OF obtaining
from it a smaller quantity which
contains unchanged percentages Of all
the constituents Of the lot.
The process used in the East Hell
ena plant varies somewhat with the
kind and quality of the ore sampled
The procedure used on each type Of
ore Is outlined below.
Weighing
All shipments Of three CD tons or
more are weighed over the Northern
Pacific Railway scales by the Northern
Pacific agent. 1t Is witnessed by the
shipper or his representative and by
the smelter weighmaster: The scale IS
q Strait, type g, with hundred (lOO)
ton Fairbanks bean sensitive TO 20
pounds. 1t Is checked several times a
year by the Northern Pacific test car
which in turn is checked against the
Master scale in st. Paul. At longer in
tervalS the scales are checked against
the United States bureau of standards
test car and at such scale tests there
is present representative of the West
ern Weighing and Inspection Bureau or
a representative of the department Of
weights and measures Of the state OF
Montana.
In addition there is a daily check on
these track scales as all bullion shipped
from East Helena is weighed twice,
first over the bullion scales in the
bullion casting department and then
over the Northern Pacific track scales.
The record Of scale tests on the North |
ern Pacific track scales has been highly
satisfactory.
In the winter time the cars are swept
clean Of snow and put in the thaW
house for q period Of "a to 70 hours
after which they are weighed and
pushed into the smelter yard for mois-
tTe sampling.
The small Shipments g tons) or less
are weighed over Fairbanks scale
sensitive to one-fourth pound which Is
located on the cutting floor OF the
sample mill.
This scale rests on a foundation en-
tirely independent Of the mill build
ing. Another Fairbanks scale sensitive
to one-fourth pound, IS located in a
special room known as the "hi-grade
room" where extremely hi-grade ship
ments are segregated and handled sep !
arately. These scales are both care
fully checked and correct weight Is as {
sTed.
Immediately after weighing the mois- I
ture sample is taken.
Moisture SampIing
As determination of the valuable
metal content of ore shipments is made
on dried samples, it is necessary to de-
termine the percentage of moisture IN
l.
lot.
All shines, concentrates, or finely di- l
vided materials are moisture sampled
by means of a pipe. On all carload lots
q series of ID holes six parallel rows OF
three, are uniformly spaced through
out: the pipe being sunk to the bottom
of the car and all of the material care
fully placed in sample buckets, after
which the sample (25 to so poundS) is
brought to the bucking room. Here the
sample is cut down and 1000 grams are
weighed into moisture pans over a
Troemner Torsion balance which Is
sensitive to 0.5 grams. This sample is
dried for "a hours Ito constant weight !
In a steam heated drying cabinet at
8 temperature of 212 degrees F. It Is :
removed when thoroughly dried and I
weighed again, the difference in weight
representing the moisture content OF
the sample. The temperature Of the !
drier is permanently recorded on 9
Bristol recording thermometer All I
samples are weighed in or out in the I
presence of the shipper or his repre-
sentative.
In the case Of crude ores, eight to t
10 holes are carefully spaced over the c
entire car and dug clear to the bottom =
OF the car by means Of q shovel. This =
material is set aside and cross sec
toned with spoon, care being taken
to get a proportion of both coarse e
and fines. Whenever possible this mois- S;
ture sample is checked against the mill p
control sample. This is not always pos &
slble because when the material is too IL
dusty, water must be put on 1t as 1t 81
passes through the mill in order to fl
protect the health of the employees. h
When the material arrives in sacks
1t is dumped out on the cutting floor lC
and If fine material pipe sample is al
obtained; if coarse material a spoon A
sample is taken. is
Control Sample u
Because of the highly spotty ten u
dency Of many gold ores, 1t is neces- %
Sary to take at least two and usually 81
four independent samples, even on u
truck lots of only a few tons. -Four Is
samples are always taken on hi-grade SC
ores q OF. gold and upWards) and fire. q
quently on lower grade ores known to d, a.
be spotty. The four samples each called "
an tx" for brevity, are prepared in ~
of the other. ~
There are three different types OF Ds
sampling the pipe sample, the shovel ~
sample, and the mill sample.
All shines, concentrates, and finely u
divided materials are sampled by the AZ
pipe. If of average values 70 holes are q
aiken in five parallel rows of IA care al
fully spaced throughout the car. This a, a.
sample weighs approximately 80 pounds a. a.
and is sent to- the cutting floor in ny
closed sample buckets. ~
When the values are higher two
samples are taken exactly as above and ~
each of these samples is handled sep
arately and independently Of each
other.
If the ore needs no crushing and is
by hand a shovel sample is r.
5aken. Every fifth shovel is set aside ID
and this one-fith is cut in half by dis 81
sarding every other shovel full This M
leaves one-tenth of the original ship q
ment for a sample and 1t is sent to
he cutting floor.
All material that needs crushing, |
which includes practically all crude ore
Is sent to the sample mill.
SampIing Mill
After the moisture sample Is taken
he lot of ore is unloaded and put
through one Of two sample mills a n,