Chibaite is a new mineral found from Arakawa, Minami-boso City, Chiba. Chibaite has framework structures with cage-like voids occupied by natural gas molecules. In Arakawa, many of chibaite crystals are altered as white pseudomorphs of quartz after chibaite. Under polarization microscope, they exhibit banding structures ranging from several tens to hundreds μm, parallel to the original external shapes of chibaite. The internal textures of pseudomorphs often seems as if chibaite and quartz are epitaxial intergrown. In addition to white quartz pseudomorphs after chibaite, there is another type of pseudomorphs that are cubic-shaped and semi-translucent. Although the cubic-shaped quartz are probably pseudomorphs after melanophlogite, melanophlogite itself has not been found in Arakawa.
