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Hall: The good, the bad, the gold, the coal

122616JoyHall

Joy Hall

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Bobby Burns

Monday, December 26, 2016

Here’s hoping you got more gold than coal in your stocking!

Both gold and coal have had moments of greatness in North Carolina. Unlike frankincense and myrrh, which are the saps of shrubs not native to our climate, gold and coal have Tar Heel history.

The United States stretched only as far west as Tennessee on the day in 1799 that young Conrad Reed found a shiny yellow rock of some heft in the waters of Little Meadow Creek east of Charlotte. That was the first gleam in the first flush of the first rush of gold in the United States. A US mint was lured to Charlotte.

Thirty-two years later, the rush rushed east, as far as Nash County, not so far from here. Sixty miles northwest up Route 43 lies the site of the Argo Gold Mine two miles to the west, and seven miles to the east is the Conyers Gold Mine location.

The gold likely bubbled out of a sluice of hot water streaming through melty rock deep underground during an ancient earthquake, when a quick shift in the placement of deep rocks briefly dropped the pressure and vaporized the lighter constituents, leaving behind a thin ribbon of gold ore.

More earthquakes along the same fault line deposited more ribbons of gold, right on top of the first ribbon, again and again, fattening the vein. Later, at the surface, wind and water would break off exposed nuggets and send them flowing down rivers, including tributaries of the Tar.

Rivers are especially good at loading lodes of gold. Moving water carries sediments: The faster the water, the more sediment it can carry. But gravity works against that: The heavier the sediment, the faster it sinks. Fast water carries almost anything, but when it slows, the densest sediment falls out first.

Because gold, as an element, is much denser than typical rocks and minerals, it tends to sink to the bottom at the slightest slow patch, such as the inside of a river bend, behind a big rock, or when the downhill slope of a stream flattens. Such was the placer gold of Argo and Conyers.

Prospectors use the same speed-water technique to pan for gold. Panners scoop up some river sediment and water, then swirl it like a centrifuge so that the gold settles down in the pan while the rocks and minerals suspend near the top, like the fat separating off the gravy. When the pan is tipped, the lightweight sands and grits on top flush out.

In 1972, Mom handed us pie pans and sent us out into the woods of Cripple Creek, Colo., to strike it rich. Cripple Creek is the home of several gold mines that have operated intermittently over the last 125 years. Nestled all snug in our beds, visions of golden plums and yellow brick roads danced in our heads. But panning is harder than it looks. Two requirements that I missed out on altogether are to make sure you are panning dirt from a loaded part of the river, and use just the right swirl speed.

Gold, by the way, looks a lot less authentic than fool’s gold. Real gold looks yellow and somewhat soupy. Fool’s gold is golden and forms dignified cubes. I found neither.

North Carolina’s coal is mostly in the Deep River area, southwest of Raleigh, sandwiched vertically between sandstones and shales. The coal is the morphed remains of peat, from ferns and logs waterlogged in a bog that existed around the time of the earliest dinosaurs.

A thousand feet below the surface, the pressure and temperature were sufficient to cook and crush the bog into a few feet of coal. To the west is granite that gurgled up as volcanic islands swept up against the precursor of North America before the dinosaurs; above is sediment that over the past 200 million years rolled off North America and sank.

Coal and gold both follow the the edge of the hard-rock boundary between the Piedmont and the Coastal Plain. Both are associated with geologic drama.

Human traditions have added a legacy of cultural drama. In the new year, best wishes for your own cultural and geological legacy!

Joy Moses-Hall teaches physics and astronomy at Pitt Community College. She has a PhD in oceanography and is the author of the novel Wretched Refuge.

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