Dauphine´ twins in quartz have been directly observed and photographed by using second‐harmonic light. A theoretical analysis shows that a plane twin boundary in a plane parallel slab of quartz produces a system of interference fringes at the crystal output surface, corresponding to the existence of two second‐harmonic beams with different directions. This was experimentally verified, and thus a topography of the twins has been obtained. Furthermore, the orientation of the twins relative to a twinless quartz crystal has been determined.