Harmotome from the Tokatoka District, New Zealand

Philippa M. Black
Department of Mineral Sciences, Smithsonian Institution, Washington, D.C. 20560, U.S.A.

Summary: Harmotome, associated with analcime, is described from andesite dykes at Rehia and Maungarahu in the Tokatoka district, New Zealand. The Maungarahu harmotome has the composition: (Na1·03K0·23)(Ba1·54Ca0·18)Al4·66Si11·31 12·39 H2O; physical properties: α 1·498, β 1·503, γ 1·506, 2Vγ 75–82° β:[001] 28° D 2·378; and cell constants: a 9· 906±0·006, b 14·119 ±0·003, c 8·712±0·007 Å, β 124° 57′ ± 3′. The harmotome is Ba-poor, and 2 Na+ has substituted for Ba2+ on a valency basis. Analcime associated with the Maungarahu harmotome has chemical composition: (Na15·16 K0·03Ca0·09)Al15·52Si32·47 15·93 H2O and physical properties: n = 1·483, D = 2·257, a = 13·708 Å. The zeolites are believed to have crystallized from Na and Ba-rich alkaline solutions at approximately 200°C. The source of the Ba is baryte concretions in adjacent limestones.

Mineralogical Magazine; December 1969 v. 37; no. 288; p. 453-458; DOI: 10.1180/minmag.1969.037.288.04
© 1969, The Mineralogical Society
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