Calle del Ónice

Onyx gives its name to this discreet street around Legazpi, beside the course of the Manzanares. The word comes from the Greek ónyx, “nail” or “claw”: its thin, translucent layers, alternating light and dark, recall the sheen of a fingernail held to the light. The mineral is a variety of chalcedony, of the quartz family: silica arranged in flat, parallel bands, white, black, or brown. When those bands curve, the same stone is called agate; when they flatten, onyx. The Romans carved it into cameos and cups, taking advantage of the fact that each layer could be polished to a different color. No record survives of why this stretch received the mineral’s name. The choice fits a habit of Madrid’s street naming: labeling modest streets with the names of gems and stones. The neighboring streets, dedicated to Bronce or Plomo, belong to the same set.