A single crystal of fully dehydrated sodium zeolite X, Na92Si100Al92O384 per unit cell, was allowed to react with rubidium vapor at 400 °C. Its structure was determined by single-crystal X-ray diffraction techniques in the cubic space group Fd3̄, a = 25.200(4) Å at 21 °C. It was refined to the final error indices, R 1 = R 2 = 0.063 with 276 reflections for which I > 2σ (I). Not only have all 92 Na+ ions been replaced with Rb+ by redox reaction, but also an additional 48 atoms of Rb were sorbed per unit cell to give Rb140Si100Al92O384. In this structure, most rubidiums participate in a cationic continuum (extends throughout the crystal) with a unit cell formula of (Rb128)80+. An additional 12 Rb+ ions per unit cell are found at the centers of double six-oxygen rings. Each supercage contains a prismatic 13-rubidium shell with a rubidium atom at its center (at the center of zeolite X's supercage). These 14-rubidium clusters, arranged in space as the carbon atoms in diamond, are tetrahedrally connected to give the continuum. Each sodalite cavity contains two rubidiums (at sites I‘ and II‘) which attach to the continuum, one per cluster, at a supercage rubidium at site II. I‘, II‘, and II are linear with inter-rubidium distances of 4.14(2) and 3.67(2) Å, respectively. Each 14-rubidium cluster plus I‘−II‘ appendage contains six valence electrons, one of which should reside principally on the rubidium at the cluster center. The remaining electrons appear to be widely delocalized as in a metal.