Where Does Your Granite Come From?

The Elberton Granite deposit is a huge mass roughly 35 miles long, six miles wide, and probably 2-3 miles deep. The total amount of granite in the Elberton area is about 6 million tons. That’s enough granite to fill the Rose Bowl almost two million times!

The Elberton Granite began 325 million years ago as a large, hot (1300-1400 degrees) mass of magma–molten rock. This magma originated when some of the earth’s crust melted–probably at a depth of about 11-12 miles. The magma rose upward and came to rest about nine miles beneath Elberton. There it cooled very slowly–taking over a million years–and solidified into granite.

That was over 300 million years ago. Since then, the granite has been pushed upward, and the land above it has been removed by erosion. The result: Now the granite lies right at the surface where it can be easily, safely, and economically quarried.

The hardest mineral on earth, diamond, has a hardness of 10. It cannot be scratched except by other diamonds. The softest materials have a hardness of 1 and are easily scratched. Few materials except precious stones are harder than 7. Elberton Granite is very hard, 6-7, and very tough to break because its tightly-bonded Quartz and Feldspar grains are made of tightly-bonded atoms. No other natural stone used for commercial purposes is any harder or more difficult to break than granite.

Granites weigh 160–220 pounds per cubic foot. That’s about the same weight as marble and only one-third as heavy as steel, but 2-3 times as heavy as concrete. Granite is heavy for much the same reasons it is so hard–the minerals within it contain tightly-packed atoms. In addition, the mineral grains themselves are also tightly packed.

Photograph taken by Mark A. Wilson (Department of Geology, The College of Wooster)

Granite has been used for gravestones and memorials for centuries. Until the early 18th century granite could only be carved by hand tools. There are a few manufacturers throughout the US who still employ highly-skilled craftsmen that create one-of-a-kind monuments by hand.

 

A key breakthrough was the invention of steam-powered cutting tools which were inspired by ancient Egyptian granite carvings. In 1832 the first polished granite tombstone was erected in an English cemetery. It caused a sensation in the London monumental trade and for some years all polished granite ordered came from one manufacturer. Granite memorials became a major status symbol in Victorian Britain.

Today, modern methods of carving include using computer-controlled rotary bits and sandblasting over a rubber stencil. Leaving the letters, numbers and emblems exposed on the stone, the blaster can create virtually any kind of artwork or epitaph on the granite headstone or granite base.