Mordenite tuff from the Itaoroshi zeolite deposit, Miyagicho, Miyagi prefecture

Abstract

Fourteen specimens of mordenite tuff from the Itaoroshi zeolite deposit, Miyagi-cho, Miyagi Prefecture, were investigated by means of cation exchange, carbon dioxide gas adsorption, X-ray diffraction, chemical analyses and Hunter's whiteness measurement. The specimens were collected from a column of the Shirasawa formation at the vicinity of the zeolite deposit. The bulk chemical composition of them is fairly homogeneous, and ranges in Si/Al ratio from 4.28 to 5.63, averaging 4.81. Equivalent content of Ca2+ surpasses those of Na+, K+ and Mg2+. The content of calcium has good correlation with that of mordenite. Also the significant correlations were recognized among mordenite content, carbon dioxide amount adsorbed, cation exchange capacity (CEC) and total value of cations leached by NH+4. The upper part of the column which is highly mordenitized bed is about 80 meters in thickness. While in the lower part, the mordenite content decreases as the depth increases. Average mineral composition of the 8 specimens collected from the highly mordenitized bed is as follows: mordenite=65.8wt.%, quartz=5.8wt.%, α-cristobalite=1.6wt.%, feldspar=3.3wt.% and amorphous materials=23.5wt.%. Their average CEC is 140.3meq./lOOg.