from translucency to transparency

Chert, flint, agate, and glassy rock can flake to a cutting edge only a few atoms thick. Prehistoric people made long oval knives of this surpassing sharpness, and made them, wittingly, too fragile to use. Some people—Homo sapiens—lived in a sub-freezing open-air camp in central France about eighteen thousand years ago. We call their ambitious culture Solutrean; it lasted only about three thousand years. They invented the bow and arrow, the spear thrower, and the needle—which made clothes such a welcome improvement over draped pelts...

Solutrean artisans knapped astonishing yellow blades in the shape of long, narrow pointed leaves. The longest Solutrean blade is fourteen inches long, four inches at its beam, and only one-quarter inch thick. Most of these blades are the size and thickness of a fillet of sole. Their intricate technique is overshot flaking; it is, according to Douglas Preston, "primarily an intellectual process"...

Hold one of these chert knives to the sky. It passes light. It shines dull, waxy gold—brown in the center, and yellow toward the edges as it clears. At each concoidal fractured edge all the way around the double-ogive form, at each cove in the continental stone, the blade thins from translucency to transparency. You see your skin, and the sky. At its very edge the blade dissolves into the universe at large. It ends imperceptibly at an atom.

Each of these delicate, absurd objects takes hundreds of separate blows to fashion. At each stroke and at each pressure flake, the brittle chert might—and, by the record, very often did—snap. The maker knew he was likely to lose many hours' breath-holding work at a tap. The maker worked in extreme cold. He knew no one would ever use the virtuoso blades. He protected them, and his descendants saved them intact, for their perfection. To any human on earth, the sight of one of them means: someone thought of making, and made, this difficult, impossible, beautiful thing.

-- Annie Dillard For the Time Being