The Black Mirror That Crossed an Ocean and Ended Up in the British Museum

In the Enlightenment Gallery of the British Museum there is a circular black mirror, about seven and a half inches across, polished to a dark shine. A handwritten note kept with it calls it the Devil's Looking-glass. Its most famous owner was John Dee, mathematician, astrologer, and advisor to Queen Elizabeth the First, and in the 1580s Dee used it for what he called angelic conversations, gazing into the black surface in search of visions. For centuries, nobody could say where the mirror itself had come from. In 2021, science answered.

Archaeologists Stuart Campbell and Elizabeth Healey of the University of Manchester ran a geochemical analysis on the mirror, published in the journal Antiquity, and matched its obsidian to a specific source: the quarries near Pachuca, in central Mexico. The most famous scrying mirror in European history turned out to be an Aztec artifact, carried across the Atlantic in the decades after the Spanish conquest. The Elizabethan court's window into the spirit world was made by artisans on another continent, for a god the court had never heard of.

The lord of the smoking mirror

That god had a name, and the name is the whole story in miniature. Tezcatlipoca, one of the great deities of the Aztec world, translates as smoking mirror, and in the codices he is depicted wearing circular obsidian mirrors on his temple, his chest, and his foot. To the Aztecs, the reflective black surface was an instrument of premonition and power. Obsidian mirrors were used for scrying, for ritual, and, in Aztec belief, as a shield against bad spirits, with the surface capable of capturing what it reflected. Drawings of mirrors almost identical to Dee's appear in the Codex Tepetlaoztoc, a sixteenth-century Aztec manuscript.

So when a Spanish ship carried the Pachuca mirror to Europe, it delivered a working religious instrument into a continent that had its own long tradition of magic mirrors, and the two traditions recognized each other instantly. Dee, the most learned man in England, looked at an Aztec ritual object and knew exactly what it was for. Nobody had to explain it to him. Some human instincts about dark reflective stone apparently need no translation.

The sharpest edge people ever made

Obsidian earned that aura honestly, because it is a strange material. It is volcanic glass, lava cooled too fast to crystallize, which means it has no grain, no planes, no internal structure to resist a fracture. Struck correctly, it breaks along curves into edges thinner than any metal blade, which is why the Aztecs lined wooden swords with obsidian blades and why cultures from the Near East onward, where obsidian mirrors appear as early as the seventh millennium BC, worked it before they worked bronze. The blackness and the edge belong to the same fact. Nothing inside the stone interrupts the light, and nothing inside it interrupts the break.

Why collectors keep it dark

Modern practice inherits all of this more directly than most stone traditions. Obsidian is kept today as a protective stone and a grounding stone, the black object that absorbs what should not reach you, and collectors who scry still reach for dark surfaces over clear ones, exactly as Dee's contemporaries held that dark stone showed the future while clear crystal showed spirits. Whether you keep a sphere on a shelf or a small tumbled piece by the door, you are keeping the domestic descendant of Tezcatlipoca's mirror, and its job description has barely changed in five hundred years.

Buying it without being fooled

The unhappy modern footnote: because obsidian is a natural glass, manufactured glass impersonates it perfectly at a glance, and much of what is sold as obsidian, especially the vivid green and blue varieties, is simply colored bottle glass. Real obsidian is nearly always black, smoky brown, or the subtle sheens of rainbow and gold-sheen varieties, and it often shows faint flow bands from the lava it once was. Perfectly uniform, brightly colored, bubble-filled material is glass from a factory rather than a volcano. The checks in our fake-spotting guide catch it, and the free 26-stone guide covers obsidian's imitators in detail.

The real thing costs little, which seems almost wrong for a stone with this much biography. A few dollars buys you the same material that armed an empire, guarded its temples, and sat on a desk in Elizabethan England answering questions nobody else would answer. Few objects in any home carry that much story per ounce.

The traditions described here are part of cultural and spiritual history. Crystals are not a treatment for any medical or psychological condition. Please read our full disclaimer.