A Geological Hike through Occoneechee Quarry

Minerals, like water, are necessary for life. Whether you realize it or not, every living being depends on them for sustenance, and their absence would quickly spell the end of our species.

This is probably why most humans have an intrinsic attraction to minerals in one way or another. Whether it’s the luster of gold, the hardness of a diamond, the utility of granite, or the softness of mica, there’s something about them that draws our attention and demands respect.

Despite this, many minerals are taken for granted, treated as bare essentials, or overlooked altogether. They’re the ugly ducklings of the digital economy, but without them we would have none of the digital devices — which are, in part, made from rare-earth minerals — that so many of us depend on.

But it’s one thing to know the value of a mineral; it’s another thing to see it for yourself.

And that’s why I decided to document my latest hike to Occoneechee Mountain, where there’s an abandoned quarry with rock formations and minerals in abundance. The most notable of these are pyrophyllite, goethite, diabase, quartz, quartzite, and schist, all of which you’ll see in this story.

Arriving at Occoneechee Mountain (625 Virginia Cates Road, Hillsborough, NC 27278) on the afternoon of November 29th, 2019, I found a parking lot full of post-Thanksgiving revelers in search of a way to burn off those five slices of pecan pie. After parking, I took to the Mountain Loop Trail and made my way over the rocky terrain until I finally reached the following sign, announcing my arrival at Occoneechee Quarry.

Making my way through a maze of pine trees and mountain laurel, I came to a relic of the old quarry itself, an apparent millrace. This would have siphoned water from the nearby Eno River to power a mill (probably a tilt-hammer mill) to pulverize stone, which was then sold to nearby businesses for fill material.

After passing though the old millrace, I reached a clearing where a large boulder sat.

To the best of my knowledge, it’s a composite of diabase and quartz, the latter of which makes up the spine of Occoneechee Mountain and provides the necessary structural support to keep the entire geological edifice from toppling into the Eno River, about three hundred feet below.

Heading on from the boulder, I came to a clearing where the first close-up glimpse of the Occoneechee Quarry came into view.

In the foreground, you can see an accumulation of rubble that resulted from a rockslide, which took place overnight between Feb. 17th and 18th, 2001, and dislodged an estimated 5100 tons of rock. This wall of rock plummeted down with staggering force, toppling trees and filling the quarry up to a height of twenty feet. Fortunately no hikers were harmed during the incident, since the park was closed at the time.

Amidst the rubble from the rockslide, there are many examples of the minerals to be found at Occoneechee Quarry, including the following fist-sized chunk of quartz, which is topped by a red ring of iron oxide.

After admiring the quartz, I got up and continued exploring.

A short distance away, I came to an exposed wall of the quarry where the underlying geomorphology was strikingly clear.

To the best of my knowledge, the white stratum in the middle is pyrophyllite, the multi-colored stratum toward the bottom left is a composite of pyrophyllite and quartzite with goethite, and the scaly outer stratum on the right is a composite of pyrophyllite and schist.

After admiring the wall of the of quarry, I followed the trail back into a thicket of mountain laurel, where I noticed the sun dropping toward the horizon.

Emerging from the mountain laurel, I found another exposed wall of the quarry with more minerals clearly visible.

Here there’s a much greater degree of unifomity, as you can see. The largest stratum is the white layer of pyrophyllite that extends from the top left to the bottom right. The smaller stratum is the blue layer of quartzite, mottled with red from iron oxide, that fills up the bottom left corner.

After passing this second wall of rock, I came around the base of another one, which appeared to have been the last active quarrying site in operation.

Of course it’s impossible to tell for sure, but the hole in the center seems to indicate the deepest point reached by workmen at the site before the quarry closed around 1908.

In the following short video, you can see the way the rock wall slopes outward at a precipitous angle and threatens to overtopple anyone who goes under it.

Honestly, it was pretty nerve-wracking to be directly underneath it. But the beauty of the blue quartzite and reddish-brown iron oxide were mesmerizing.

After exploring the precipitous rock wall, I noticed that the sun was nearing the horizon and decided to call it a day. Retracing my steps, I passed through the thicket of mountain laurel, by the rubble of the 2001 rockslide, and through the old millrace.

When I got back to the quarry entrance, I turned around and admired the view.

Heading back to my car, I thought about how the experience of seeing an actual quarry in the flesh has changed the way I look at minerals, both the ones that go in our digital devices and the ones that go in our bodies. I thought about how the underbelly of the mountain, the circuitry of my phone, and even my own skeleton are composed of many of the same elements. I thought about how we’re all made of the same star dust; how we all come from the same source; how we all share a common future.

And that future is this planet, without which neither Occoneechee Mountain, nor my phone, nor any human life would exist.

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