Abstract
The low-density cubic form of silica (impure), melanophlogite, has a clathrate-type structure that incorporates organic molecules, including long straight-chain hydrocarbons. The structure is analogous to that of the clathrate crystalline hydrates of composition 6X·46H2O or 8X·46H2O. This is the first known example of a silicate framework structure with the pentagonal dodecahedron as a framework element.