crystal structure of <a href="https://en.wikipedia.org/wiki/copper(I)_oxide" class="extiw" title="en:copper(I) oxide">en:copper(I) oxide</a>
<a href="//commons.wikimedia.org/wiki/User:Orci" title="User:Orci">Orci</a>
CC BY-SA 3.0
Eigenes Werk (own work), created with diamond 3, source: K. Ishikawa, T. Isonaga, S. Wakita, Y. Suzuki: <i>Structure and electrical properties of Au<sub>2</sub>S</i>. In: <i>Solid State Ionics</i>, 1995, 79, S. 60–66.