日本ゼオライト学会　刊行物 Publication of Japan Zeolite Association

The relationship between zeolites and host rocks seems to be different, according to genesis of zeolites. The host rock of "zeolitic rocks" which are mainly formed by diagenesis and contact metamorphism is restricted to rhyolitic to dacitic volcaniclastic rocks and related ones. While, the host rock of large-crystalline zeolites which are mostly formed hydrothermally is various-igneous, volcaniclastic, metamorphic and sedimentary rocks. The most common one is basalt flows which contain a large amount of amygdals and cavities within pillows, breccias and matrix. Alkalic rocks seem to be the favourable host rock for some zeolites such as analcime.

Recently, zeolites occuring in clastic sediments were found in Neogene formations of the Fossa Magna Region, central Japan. Zeolites mainly occur as filling in faults, fractures and joints, and sometimes as veinlets.