How much gold can prospectors find in Washington's rivers and streams?

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Nov. 20 2008 6:36 PM

The Evergold State

Are prospectors crazy to be dredging in Washington's rivers and streams?

Gold in a miner's pan
Gold in a miner's pan

Gold prospectors in the state of Washington are up in arms about new restrictions on when they can search for gold. The rules, issued last week, are intended to limit digging and dredging in streams, which may put fish eggs at risk. Just how much gold is in those Pacific Northwest streams?

It's hard to know for sure, but don't expect a Washington gold rush anytime soon. According to the most recent estimates (PDF) by geologists with the U.S. Geological Survey, the Evergreen State had about 519 metric tons of known gold resources within its borders during the late 1990s; another study guessed that there might be 2,100 tons worth of undiscovered gold deposits throughout the Pacific Coast region. Washington ranks among the top 10 states in its existing gold deposits, but it is well outpaced by Nevada's 6,100 metric tons of gold deposits, by far the largest in the nation.

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With gold prices at about $747 an ounce on Thursday, 519 tons is a significant haul. (It's $13.7 billion, to be exact.) But while no one keeps exact figures, it's hard to imagine much of that gold will show up in the pans of prospectors. Most gold that appears in streams is placer gold, which refers to gold found in the sand and gravel deposits of stream beds or beaches. (The word placer comes from the Spanish for "sand bank"; by contrast, gold that is still in solid rock is called "lode gold.") The USGS estimates (PDF) that about 20 percent of U.S. gold deposits are placer gold. But in most places—Alaska is a rare exception—placer gold is not very economical to mine, so it accounts for a much smaller percentage of gold produced nationwide. Indeed, even for a small-scale prospector, mining in a stream can get rather expensive: The suction dredges at issue in the new rules—machines that pull up material at the bottom of streams and then filter it—will set you back a few thousand dollars apiece.

The best indicator of the amount of gold in Washington's streams is probably the fact that according to the state's geology department, there isn't a single commercial placer gold operation in the state—the prospectors are all part-timers. Geologists don't offer much encouragement about the prospects of striking rich through prospecting, either. A USGS guide to prospecting notes that "[t]he grizzled prospector with a burro is no longer a significant participant in the search for mineral deposits, and the small producer accounts for only a minor share of the total production of metals including gold." Another primer from the California Geological Survey (PDF) estimates that one in every 1,000 prospectors "will ever make a strike." And in Washington—where an estimated 2,000 to 2,300 people might call themselves prospectors—the miners say that half an ounce of gold (or about $373 worth) is a pretty typical haul for a season, and that many prospectors are lucky if they find enough gold to cover their expenses.

Got a question about today's news? Ask the Explainer.

Explainer thanks Micheal George of the U.S. Geological Survey, Dave Norman of the Washington State Department of Natural Resources, and Bill Thomas of the Washington Prospectors Mining Association.

Jacob Leibenluft is a writer from Washington, D.C.