Let us consider what the Gem Rock web site is telling about natrolite with more detail, regarding properties and applications. First, we propose the structure of natrolite as given by In the introduction of their article, Paczwa and coworkers stress that the "physical properties of materials entrapped in nano-sized cavities [are] of significant interest for both fundamental science and application of nano-porous compounds. The mineral natrolite is a typical porous compound (zeolite) with the narrow nano-channels". As previously told, natrolite is orthorhombic, space group Fdd2, with formula units Na2Al2Si3O10•2H2O. In its framework we find "tetrahedra of alumina (AlO4) and silica (SiO4) chains linked together via common oxygen atoms". "The natrolite structure contains channels running parallel to the c-axis and channels connected among themselves by oxygen windows. These oxygen rings create a system of channels, which are placed perpendicular to c-axes" . "The water molecules and sodium ions form zigzag chains along the channel parallel to c-axis. Water molecules occupy two sites in the channels and the other sites are occupied by sodium ions. Each water molecule is coordinated by two framework oxygen atoms and by two sodium ions" . "One of the main features of natrolite is a narrow diameter of channels. The diameter of the oxygen's windows in the [110] direction is 2.60 A, but the diameter of channel paralleled to the c-axis is only 2.08 A, and it is less than 2.8 A, which is usually assumed for the diameter of water molecule" . "Therefore, the interesting problem is the determination of the microscopic mechanism of water molecules mobility in the natrolite channels. The mobility of the water molecules in natrolite was studied … [see references in Paczwa and coworkers]. … the main kind of mobility of water molecules at high temperature in natrolite is the diffusion along channels parallel to c-axis and water molecule jumps without breaking of one chemical bond of water molecule with sodium ion". Paczwa and coworkers explain that water molecule motion is a "hopping" motion: "the water molecules spend most of their time in a potential well corresponding to equilibrium positions, and only a very small fraction moves between these potential wells" .