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i
ees

79

Table XII.—Fineness and Absorption of
Diatomaceous Earths.

Total percentage retained on sieves. 1 2 3 4 5 6 7
iene 7 1 4 12 2 12 9
PIG MCS ee 11 5 11 28 4 84 20
: WOO meshin. Sea eS 38 47 68 70 34 65 50
Pascine 200: mesh |. = - 0. 62 53 32 30 66 35 50

Absorption. Cubic centimetres ab-

sorbed by 100 grains of earth.... 113 130 118 127 141 133 128 ;

Howells Frechette, Mines Branch, reports as follows in regard to
methods employed by him in making these tests.

‘“‘The crude material was firmly coherent and difficult to break down
without at the same time breaking the integral grains. Great care was
taken during the crushing not to overgrind the material, therefore it is
altogether likely that the percentages shown retained on the larger screens
do not cepresent coarse grains but rather uncrushed particles of the original
ageregate. Due to the angularity of the particles and their light weight,
the material fluffs and forms small pellets on the screens, which are difficult
to overcome. Therefore, the percentages of the material passing through
the 150-mesh and retained on the 200-mesh screens are higher than they
should be. In other words, it is probable that the percentages shown of
material passing through the 200-mesh screens are lower than they should
be in all cases.

“The following method was used to obtain figures to represent the capa-
city of the several samples for absorbing liquids. On the addition of water
to the powdered material it was readily absorbed and a sample first became
roughly coherent though crumbly. As the water content increased, the
sample suddenly lost its ‘‘shortness’? and became slightly plastic and
could be considerably deformed with a spatula without showing cracks.
Check tests showed that the amount of water necessary to attain this
cond.tion was practically the same for any one sample. The amount of
cubic centimetres of water absorbed by 100 grains of the material when
at this conditioa was used as a measure of the absorption.”

High absorption probably indicates large percentage of diatoms

_ relative to that of clay and other impurities in the earths. Sample No.

2, for instance, which is higher in silica and lower in impurities than samples
1 and 3, has also a higher absorption. If this conclusion be correct the
material on the bluffs (Figure 12, localities 1, 2, and 3), is of somewhat
higher grade than that at locality 11, Figure 12.

Commercial Development.

The deposit southwest of Quesnel (Figure 12, locality 11) lies near the
summit of an east-facing hill at an altitude of 800 feet above the level of
the Fraser. The outcrop, about 100 feet in length and 40 feet high (Plate
XIV), is covered by debris in both directions along the strike. In the
direction of dip-it is overlain by 3 feet of gravel and 7 feet of basalt, and
farther in this direction the hill rises for 35 feet, partly slide material and

5172—6}

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