Lake of Fire by Frank Belknap Long

Steve found the mirror in the great northwestern desert. It was lying half-buried in the sand, and the wind howled in fury over it, and when he bent to pick it up the sun smote him like a shining blade, dividing his tall body into blinding light and wavering shadow.

I knew it was a Martian mirror before he straightened. The craftsmanship was breathtaking and could not have been duplicated on Earth. It was shaped like an ordinary hand mirror; but its glass surface was like a lake of fire, with depth beyond depth to it, and the jewels sparkling at its rim were a deep aquamarine which seemed to transmute the sun-glow into shimmering bands of starlight.

I could have told Steve that such mirrors, by their very nature, were destructive. When a man carries a hopeless vision of loveliness about with him, when he lives with that vision night and day, he ceases to be the undisputed master of his own destiny.

“She’s alive, Jim,” Steve said. “A woman dead fifty thousand years. A woman from a civilization that flourished before the dawn of human history.”

“Take it easy, Steve,” I warned. “The Martians simply knew how to preserve every aspect of a mirrored image. Say howdedo to her if you like. Press your lips to the glass and see what happens. But don’t mistake an imitation of life for the real thing.”

“An imitation of life!” Steve flared. “Man, she just smiled at me. She’s aware of us, I tell you.”

“Sure she is. Her brain was mirrored too, every aspect of its electro-dynamic structure preserved forever by a science that’s lost forever. Get a grip on yourself, Steve.”