Mt. Airy, NC: 1743,1889-2025 World's Largest Open Faced Quarry Closed, It Provided Granite

(Satellite)

polycor_blog

"This quarry was first operated in 1743, well before the Revolutionary War, by the Brothers of the Moravian Church who came to this region from Germany. Operations were limited in those days because of the lack of equipment and technology. The ownership of the quarry site passed through many hands over the next hundred years until 1889, when the Cape Fear and Yadkin Valley Railroad was built from Greensboro to Mount Airy. Mr. Thomas Woodroffe was selected to build the railway stations along the new rail line, and he decided to use the stone from the Mount Airy Quarry. He organized the North Carolina Granite Company May 14, 1889, and purchased the quarry site. The quarry has been in continuous operation ever since. [until 2025, see below]" [polycor]

Granite from this quarry replaced the marble sheets on the Aon Center in Chicago. (The marble sheets warped and cracked in the Chicago weather and started to fall off the building.)

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Marble was chosen because the architect wanted a white surface. The marble product "flamed" was close to white.

polycor_stones_flamed
Flamed

"In the late 1980s, this instantly recognizable part of the famous Windy City skyline faced a problem: the Carrara marble panels on the 83-story building were cracked and buckling and in need of replacement after only 15 years. In fact, the building hadn’t even completed construction when the first panel of marble cladding came crashing down to the street below. White Mount Airy Granite® was chosen as the replacement stone because it can stand up to Windy City weather while retaining white, brilliant luster over time. Today, the Aon Center is the third largest building in Chicago, and the world’s tallest granite clad building."  [polycor_blog]

The Arlington Memorial Bridge is clad with the Sandblasted product.

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Sandblasted

"The neoclassical bridge, whose original construction was launched in 1925, underwent a massive rehabilitation project starting in 2018, where hundreds of pieces of stone were removed from the historic span and were cleaned and repaired. While the original balusters were handcrafted, replacements for the few that couldn’t be repaired were made with high-tech guidance from computers, seamlessly matched with stone from the same quarry. It’s an astounding testament to the stone’s integrity that blocks mined from Mount Airy nearly a century ago match perfectly with stone extracted today." [polycor_blog]

NorthCarolinaMuseum
"Granite from the 90-acre quarry (the largest open-faced quarry in the world) is pure in color and texture; a piece removed today matches a piece removed a century ago."

"NCGC has continued to grow and evolve with the technology and markets. Today, NCGC is honored to be a part of the Polycor family of brands, having been acquired by the world’s largest dimension stone quarry company in 2021. Nothing has changed from an operations and service perspective, and you can continue to expect the same level of quality and trust that has been NCGC’s foundation and which is shared by Polycor across all of its family of brands." [polycor]

But four years later the quarry was closed at the end of Aug 2025!  [mtairynews]

I'd say that was a change. So, were they lying in 2021 or that ignorant of the economics? Either way, it is a rather low "level of trust."

The mother mass is "is about 7 miles long and 1 mile wide, north and south. And it’s 8,000 feet deep." They have mined just 60' down. They estimate that they have enough granite to last another 500 years. The mining process uses a water pressure jet at 40,000psi, a diamond saw and explosives (Primacord). [OurState]

About 336 million years, to be precise. It was then that The Rock formed through a geological process called plate tectonics.

“Our planet is a restless planet,” says Bert Meijboom, a Pilot Mountain geologist who does consulting work for the North Carolina Granite Corp. and is familiar with the granite quarry. “Continental plates are constantly on the move.”

North Carolina sits on the North American plate, Meijboom says. Several times in geological history — remember, we’re talking about millions of years here — that plate has collided with the African Plate. The last time it happened — approximately 360 million years ago — portions of the African plate subsided beneath the North American plate, creating a subduction zone that set the stage for the formation of Mount Airy’s huge granite quarry.

“It was along such a zone, some 12 to 25 miles underneath the American plate, that blobs of molten rock were formed,” Meijboom says. “Due to its relatively lighter weight, the molten rock, also called magma, started to rise toward the surface, intruding the upper portions of the plate.”

The magma slowly solidified over millions of years and formed what’s known as a pluton — basically, a body of igneous rock that develops beneath the earth’s surface. As the plates continued to move and extensive erosion occurred, these plutons — one of which geologists actually refer to as the Mount Airy pluton — appeared at the surface, giving The Rock its designation as an open-faced quarry.

[OurState]

 This is what motivated my research.

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