Atop the Washington Monument, a pyramid from N.C.

One reason aluminum was so costly [in 1884] was because it was essential to use the highest purity aluminum oxide available, which happened to be corundum….

“The best crystals were being mined commercially in the gravels, stream beds, mountain sides and soils of the Carolinas, mostly in the Cowee River Valley of Macon County, North Carolina.

“Crystals of corundum are more familiar to us as sapphires and rubies. Rubies are the red ones. Any other color is called sapphire. They are the same gemstones  rockhounds have been seeking at Carolina gem mines every summer for years…..

“Next to diamond in hardness, corundum crystals at that time were being used primarily for manufacture into ‘jewels’ for watches and other instruments requiring precision, wear-resistant bearings. Some were fine enough to be fashioned into jewelry,  which was why Tiffany’s operated some of the deposits. Some were crushed and used as coatings on ’emery’ paper.

“And some were used as the ‘ore’ for smelting that new metal, aluminum, which possessed the special properties the builders of the Washington Monument found so attractive [for constructing its pyramid-shaped cap]….”

— From  What does the Washington Monument have to do with the gems of North Carolina?”  by Dr. Philip Garwood at the Cape Fear Community College Department of Geology (Oct. 8, 2012)

The monument reopened to the public today, nearly three years after suffering earthquake damage.