Melanophlogite from Kisarazu, Chiba, Japan

Abstract

Melanophlogite is a silica mineral having framework structure with cage-like voids occupied by gas molecules such as CH₄, CO₂, N₂. Melanophlogite has never been found in Japan, even though some cubic-shaped quartz, which are probably psudomorphs after melanophlogite, have been found. Here, we report discovery of melanophlogite from Kisarazu, Chiba Prefecture. It was found in cracks of tuffaceous breccia in the Pleistocene Shimousa Group. It occurs as transparent cubic crystals of sizes up to 0.1 to 0.2 mm. X-ray powder diffraction patterns of the sample measured by Gandolfi camera are consistent with the tetragonal phase of melanophlogite. The lattice parameters refined by the Rietveld analysis are a=26.8357(8)Å, c=13.3690(8)Å.