Strontian hollandite in a quartz schist from the Saruta-gawa area in the Sanbagawa metamorphic terrain, central Shikoku, Japan

Abstract

Strontian hollandite (up to 3.45 wt.% SrO) is found to occur in a piemontite-bearing quartz schist of the Sanbagawa metamorphic terrain in central Shikoku, Japan. Hollandite occurs as an aggregate of fine crystals (up to 100 μ m long) associated with braunite. From the central part of the aggregate outward, its BaO, Fe₂O₃ and TiO₂ contents increase and its MnO₂, K₂O and SrO contents decrease. Chemical variation in the hollandite suggests K (Mn⁴⁺, Ti⁴⁺)⇔(Ba, Sr)Fe³⁺ substitution. Hollandite is tetragonal or pseudotetragonal, and lattice constants are a=9.90(4) Å and c=2.87(5) Å.