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CHAPTER XIV.

WHAT I LEARNED ABOUT THE MINERALOGY OF OREGON.

The valuable minerals which have been worked in Oregon are: first, the precious metals, gold and silver; and, second, copper, lead, iron, coal, marble, and salt.

Concerning the formation of the metals, more especially of gold, there are many theories. The age of the rocks associated with gold must serve as an indication of some value in pointing out its origin,—the most probable theory of which seems to be that, at a period when great changes were going on in the shape of the earth, the upheaval of mountains and overflow of volcanoes, certain vapors contained in the earth being forced by heat and pressure into the fissures of rock already hardened, or even into the substance of rock not yet solidified, became precipitated in the form of gold upon the walls of the cavities which shut them in. Much of this gold was subsequently set free by the action of the water, and is found mixed with sand and gravel or earthy matter in old river-beds or valleys between high mountains. Much of it still remains in its original position, and has to be got out of the rock by blasting and crushing.

The gold-fields of Oregon lie along the bases of, or in close neighborhood to, its mountain ranges; and there is no mountain chain which has not somewhere along it a gold-field, more or less productive ; but in West Oregon their rugged nature and impenetrable covering of timber have prevented their being much prospected. It is only in the placer diggings of the southern counties and the beach diggings of the coast counties that mining for gold has been carried on to any extent.

After the rush of ’49 to the gold-bars of the California rivers had made miners and experts of a hitherto purely agricultural population in Oregon, they began to find indications on their own soil of the existence of the precious metal. Travelling overland to and from California gave them opportunities of observing the nature of the country, and it was not long before the gold- hunters stopped north of the California line. As early as 1852