Worlds Largest Granite Quarry, Mount Airy, nicknamed “The Granite City,” is home to the largest open face granite quarry in the world operated by the North Carolina Granite Corp. There are larger pit quarries throughout the world but no larger open face quarries. A pit quarry is below the surface, while an open face quarry is at ground level. Many of Mount Airy’s homes, churches and businesses are made from Mount Airy granite.
Shaped like an enormous oyster shell, the quarry covers approximately 90 acres, which is currently under operation. The deposit is about 1 mile long and 1/3 mile wide. Geological mapping shows the total mass to be about 7 miles by 4 miles and 6,000 to 8,000 feet deep. Since 1889, the quarry has been in full operation, and the surface has only just been scratched according to depth tests. Geologists say the deposit can be quarried for approximately 500 more years without exhausting the supply.
Because the granite has no natural beds and cracks, it is necessary to free great sheets of granite from the mass by a process called lifting. Dynamite is never used for quarrying. The results of its use would be disastrous because its force would shatter and crack the granite, which would cause flaws. Instead, black gun powder is used.
The story goes that the world’s finest natural quarry changed hands for nothing! In 1872, a farmer named John Gilmer purchased several thousand acres of farm and woodland covering what is now part of Mount Airy and much of the Flat Rock community. One of his friends learned the tract of land contained 40 acres of bare rock. Mr. Gilmer immediately went to the seller and threatened to back out on the deal because of the worthless 40 acres. The seller agreed to deduct the 40 acres of worthless rock in calculating the dollar value of the whole tract. Therefore, the quarry exchanged hands for nothing.