Editing Gold rush (section)

==Surviving the gold rush==

[[Image:Wooden gold sluice in California between 1890 and 1915..jpg|thumb|A man leans over a wooden sluice. Rocks line the outside of the wood boards that create the sluice.]]
[[File:NMA.0039209 Emigration. Svenskar i Amerika. Guldvaskare vid Black Foots River, Montana.jpg|thumb|Swedish gold panners by the [[Blackfoot River (Montana)|Blackfoot River]], [[Montana]] in the 1860s]]
[[File:Kullanhuuhdontaa Ivalossa.jpg|left|thumb|upright|Gold prospecting at the [[Ivalo River]] in 1898]]
[[Image:Hydraulic mining in Dutch Flat, California, between 1857 and 1870.jpg|thumb|Jets of water at a placer mine in [[Dutch Flat, California]] sometime between 1857 and 1870]]
Within each mining rush there is typically a transition through progressively higher capital expenditures, larger organizations, and more specialized knowledge.

A rush typically begins with the discovery of [[placer gold]] made by an individual. At first the gold may be washed from the sand and gravel by individual miners with little training, using a gold pan or similar simple instrument. Once it is clear that the volume of gold-bearing sediment is larger than a few cubic metres, the [[placer mining|placer miners]] will build rockers or sluice boxes, with which a small group can wash gold from the sediment many times faster than using gold pans. Winning the gold in this manner requires almost no capital investment, only a simple pan or equipment that may be built on the spot, and only simple organisation. The low investment, the high value per unit weight of gold, and the ability of gold dust and gold nuggets to serve as a medium of exchange, allow placer gold rushes to occur even in remote locations.

After the sluice-box stage, placer mining may become increasingly large scale, requiring larger organisations and higher capital expenditures. Small claims owned and mined by individuals may need to be merged into larger tracts. Difficult-to-reach placer deposits may be mined by tunnels. Water may be diverted by dams and canals to placer mine active river beds or to deliver water needed to wash dry placers. The more advanced techniques of [[ground sluicing]], [[hydraulic mining]] and [[Gold dredge|dredging]] may be used.

Typically the heyday of a placer gold rush would last only a few years. The free gold supply in stream beds would become depleted somewhat quickly, and the initial phase would be followed by prospecting for veins of [[lode]] gold that were the original source of the placer gold. Hard rock mining, like placer mining, may evolve from low capital investment and simple technology to progressively higher capital and technology. The surface outcrop of a gold-bearing vein may be oxidized, so that the gold occurs as native gold, and the ore needs only to be crushed and washed (free milling ore). The first miners may at first build a simple [[arrastra]] to crush their ore; later, they may build [[stamp mill]]s to crush ore at greater speed. As the miners venture downwards, they may find that the deeper part of vein contains gold locked in [[Sulfide mineral|sulfide]] or [[telluride mineral]]s, which will require [[smelting]]. If the ore is still sufficiently rich, it may be worth shipping to a distant smelter (direct shipping ore). Lower-grade ore may require on-site treatment to either recover the gold or to produce a concentrate sufficiently rich for transport to the smelter. As the district turns to lower-grade ore, the mining may change from underground mining to large [[open-pit mining]].

Many [[silver rush]]es followed upon gold rushes. As transportation and infrastructure improve, the focus may change progressively from gold to silver to base metals. In this way, [[Leadville, Colorado]] started as a placer gold discovery, achieved fame as a silver-mining district, then relied on lead and zinc in its later days. [[Butte, Montana]] began mining placer gold, then became a silver-mining district, then became for a time the world's largest copper producer.