CELADONITE IN THE TUFF OF OYA, TOCHIGI PREFECTURE, JAPAN

Abstract

Celadonite occurs as an alteration product of glass fragments in rhyolitic tuff at Oya, Tochigi Prefecture. The chemical composition: SiO₂, 55.99%; TiO₂, 0.49%; Al₂O₃, 11.13%; Fe₂O₃, 4.65%; FeO, 7.34%; MnO, 0.20%; MgO, 2.27%; CaO, 0.22%; Na₂O, 1.30%; K₂O, 8.00%; H₂O⁺, 4.22%; H₂0^-, 3.68%; total, 99.50%.
The structural formula:
(K_0.73Na_0.18Ca_0.02) (Mg_0.30Mn_0.01Fe²⁺_0.44Fe³⁺_0.25Al_0.93) (Si_3.99A1_0.01) O₁₀ (OH)₂.
Although the amounts of Al₂O₃ and FeO are slightly larger than in earlier data, the Oya specimen is identified to be celadonite from its mode of occurrence, X-ray powder pattern, i. r. absorption spectrum and DTA curve.