ROCKS & MINERALS

near Beatty, Nye County, NevadaMarch 24, 1988
 
NEVADA: Nye County
 
Just north of NV Hwy 58, about six miles southwest of Beatty

Exiting Death Valley, just a few miles east in Nevada, I found a dirt road wandering into the desert, ending inside a random scattering of boulders, at an elevation of about 3300 feet. For a while I just sat empathizing with Creosote-bushes and trash, letting the buzz of all the tourist stuff in Death Valley dissipate.

On this first morning in Nevada I resolve to prepare "Bird List #4"  but I can't spot enough species to constitute a real list. After an hour of looking, my list mentions only Ravens, Rock Wrens, House Finches and Black-throated Sparrows. The bird that could have been our first migrant gets away. It's a hummingbird, but all I see of it is a fast-moving silhouette. In the East, except in southern Florida, hummingbird identification is easy because we have only one species but in this area, maybe four are possible.

Breaking off the bird-walk, I climb a nearby peak. The climb turns out to be much more difficult and risky than I'd anticipated, but the view teaches a great deal. I can see that this is mining country. In the past, silver and gold have been mined here. Across the valley an old mine-shaft entrance big enough to walk into upright is visible. On several slopes around me test pits have been dug. The rock debris below one Henry-sized test-pit is greenish while not twenty feet away the debris below a similar hole is dark rusty-gray, indicating that the two pits were dug into different strata. About a mile to the west, up our valley, a back-hoe, several pickup trucks and a house trailer parked next to a large pile of tailings indicate an operating mine.

Right above Henry a five-foot tall, six-inch wide, white pipe sticks from the ground. I've been imagining that maybe an amateur rocket-maker has been here, using the pipe in test-firings. But from this height I see that the pipe is just one of several being used to establish boundary lines -- claims -- for mineral rights. And now for the first time I realize that Henry himself is parked in an old stripmine. The ridge behind him is a mound of tailings and the rock wall to his left is the highwall.

The ghost town of Rhyolite lies right over the next ridge. Remembering back to my undergraduate days at Western Kentucky University, I visualize Minerology Lab's rock tray holding the thirty or so rocks we were expected to learn to identify. Rhyolite was a fine-grained rock of volcanic origin -- one with the same minerals as granite but in different proportion. It's made of quartz (SiO2), orthoclase feldspar (KAlSi3O8) and a few grains of dark minerals, such as mica, amphibole and pyroxene.

In the desert where vegetation doesn't mask the surface geology it's easy to get interested in rocks and minerals. Just among the small group of old fishermen at Amistad, four considered themselves to be rock hounds. Often these men's talk would slip from the subject of fish to lavish descriptions of certain geodes they'd found, or to good examples they'd seen of "Texas plume agate" or sky-blue topaz. One morning as I walked along Amistad Reservoir I met a paleontologist and his wife fishing. The woman was a Mescalero Apache Indian and when she decided that she liked me she gave me an "Apache tear," a naturally tear-shaped form of a black, shiny stone called obsidian. "It'll bring you luck," she said. "But only if it's given to you, and not sold." She was very serious in presenting the gift. Later her husband told me that I had been honored and that the gift was not to be taken lightly.

As I sit typing this, I try to interpret the immediate landscape seen through Henry's door. The jagged peak right in front appears to be an ancient volcano's pipe up through which lava escaped during an eruption. Rock surrounding the ancient volcano has eroded away leaving these fingers of basaltic rock jutting maybe fifty feet above the surrounding talus. Below this "volcanic neck" rises a ridge composed of horizontal strata. The strata's dominant colors are creamy white, pale pink, slate gray and sometimes pale greenish. I'm interpreting each of these layers as composed of ash ejected during various eruptions. The different colors result from the chemical composition of ash from one volcano differing considerably from that of another -- different chemicals create different-colored rocks and ash. Greenish strata may have some copper in them and maybe the pink ones have manganese.

In one place a vertical wall of dark basaltic rock cuts through horizontal strata of ash. This is a volcanic "dike."

During the eruption, or near-eruption, of an ancient nearby volcano, such upward-pushing force was developed below us that the overlying strata, these ancient layers of ash, fractured, as might horizontal layers of glass if something pushed on them from below. Then upward-surging magma intruded into the ash-strata's vertical cracks. Later the magma hardened into rock that was not as easily eroded by wind and rain as the surrounding layers of ash. What once was molten lava extruded into a crack now is a dark wall twenty feet high ranging across the valley floor.

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