Abstract
Four ammonium sulfate minerals, i.e., boussingaultite, godovikovite, efremovite and tschermigite, were found from coal gas escape fractures at Ikushunbetsu, Mikasa City, Hokkaido, Japan, on the field survey in 2009. The minerals were identified using XRD, SEM-EDS, XRF and/or CHN analyses. This is the first occurrence of these four mineral species in Japan. Godovikovite is the most common species in this survey and has Al/(Al + Fe3+) ∼ 0.9. The mineral coexists with efremovite. These usually occur as very fine admixtures (<10 μm) forming porous crust up to several millimeters in thickness. Boussingaultite [Mg/(Mg + Fe) = 0.96 to 0.97] occurs as aggregates of platy crystals up to 1 mm in diameter and 0.2 mm in thickness or as very fine admixtures (<10 μm) with tschermigite forming porous stalactitic-like aggregate. Godovikovite, efremovite and boussingaultite were formed as a primary sublimate from coal-gas. Tschermigite is considered to be a hydration product of godovikovite.
