October 28, 1863: Waldo, Oregon
I spent [today] here and rode out ten miles to visit a quartz mine, the only one worked in this region. The principal owner and manager is a very intelligent young German, who treated us very kindly. The quartz is crushed and gold extracted by arrastra, the old Spanish method. The machinery consists of a sort of large shallow tub, about twelve feet in diameter and two feet high, the staves of thick plank, the bottom of stones firmly laid in a solid formation. In the center there is an upright shaft with four arms, like the arms of an old-fashioned cider mill. These are stout and short, and to each one several rocks, each weighing several hundred pounds, are fastened by chains. The whole is driven by water power. The quartz is broken with hammers into pieces as large as apples, and several hundred pounds are thrown in this tub with water. The heavy bowlders are dragged over them, grinding and crushing, finally reducing the material to a pulp like thin mush. There is some quicksilver always in the bottom, which runs into the hollows between the stones of the bottom or bed and dissolves most of the gold. After it is thoroughly pulverized it is run through a trough about a foot wide with water in a shallow stream. On the bottom of these troughs are coarse woolen blankets, in the hairs of which the fine particles of gold are caught. Every few minutes these blankets are washed in a large tub of water, which removes this gold.
In this way about twenty-five dollars of gold is extracted from each ton of rock crushed, which is probably scarcely half that it contains. The process is a crude one, and its only recommendation is its cheapness, as a mill of this kind can be built for $2,000 to $5,000, while an improved mill, with stamps, such as I described in a previous letter, costs from $15,000 to $150,000, according to the size and the locality, cost of freight, etc.