\ =: 76

formation at Quesnel, were first faulted and brecciated and afterwards
turned to clay, so that the clay-forming processes were active after the
extrusion of the Lower Voleanics. The evidence, therefore, indicates that
the period of clay formation, if it be assumed there was only one such -
period, antedated upper Miocene time and post-dated a period of faulting.
This period of faulting must have followed soon after the extrusion of the
Lower Voleanics, and, therefore, the formation of the clays can be ascribed
to heated solutions and vapours derived from the same source as the lava
and rising to the surface after the lava eruption.

“

CHAPTER VI.
DIATOMACEOUS EARTH, LIGNITE, PERIDOT, AND
MUSCOVITE. |
3 DIATOMACEOUS EARTH.

Deposits of diatomaceous earth were examined in the vicinity of
Quesnel. Diatomaceous earth is the name given to deposits that are
usually white or cream-coloured, and consist wholly or in part of the
siliceous tests of low forms of plant life known as diatoms. These tests
or shells are very Ininute, the largest smaller than a pin head, the average
visible only under a high-power microscope. They are composed wholly —
of hydrous silica and contain a great many small pores arranged in intricate
patterns. The chemical composition, minute size, hardness, and porosity.
of the tests, have made the earths composed of them useful in a number
of ways. The coherent earth, reduced in a manner which will not destroy
the tests themselves and separated into powders of varying fineness, is
used largely as an abrasive and polishing agent in metal polishes, soaps,
metal powders, match heads, ete. The purer products are used in the
manufacture of siliceous glazes and waterglass or silicate of soda. The
large amount of pore space within the tests prevents the passage of heat
through the loosely packed earth or through blocks and bricks made of it.
This property, combined with the ability to stand great heat without
fusion, makes the earth of great use as insulating linings for furnaces,
ovens, safes, as well as in the walls of cold storage receptacles. It has also.
been used as an absorbent for corrosive liquids, liquid manures, and nitro-
glycerine, and for many other purposes.! ”. :

OCCURRENCES AT QUESNEL.

Deposits of diatomaceous earth occur in a cliff-face 2 miles southwest
of Quesnel (Figure 12, locality 11, and Plate XIV), also 2 miles farther up
Fraser river (Figure 12, locality 5), and a number of deposits occur.on top
of the river-cut cliffs on the big bend of the Fraser 8 miles north of the
village (Figure 12, localities 1, 2,3). All these localities are west of Fraser
river. A small lens of the earth is exposed in the brick-yard at Quesnel and
there are a few other unimportant occurrences near the river (Figure 1,
localities 6, 7, and 9).

‘A 1Boeck, Percy A., ‘“The Kieselguhr industry,’’ Metall. and Chem. Eng., vol. XII, No. 2, Feb., 1914, pp. 109-

2Frechette, Howells, ‘‘Report on the non-metallic minerals used in the Canadian manufacturing industries,
Mines Branch, Department of Mines, Ottawa, 1914, pp. 105, 107.

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