Under a cloudy winter sky, the eastern slope of Mount Arteni has the dull monotone of a barren wasteland. At 6,715 feet, its spare crest is dwarfed by the snow-capped 13,419-foot summit of nearby Mount Aragats, the highest point in the Republic of Armenia. The only signs of life are ragged clumps of wild grass, bent horizontal in a frigid wind from the high Caucasus.

Then the clouds suddenly break, and Arteni explodes into a dazzling mosaic of sunlit mirrors. Every square foot of ground, as far as the eye can see, is carpeted with fragments of glassy obsidian, many of them chipped and flaked into razor-sharp weapons and tools.

“We are looking at the remains of a gigantic open-air workshop,” says