Pseudoleucite in a Tinguaite from the Bearpaw Mountains, Montana

1 February 1960

journal article
Published by Oxford University Press (OUP) in Journal of Petrology

Vol. 1 (1) , 86-98
https://doi.org/10.1093/petrology/1.1.86

Abstract

The article presents chemical analyses of the pseudoleucite and groundmass of a pseudoleucite tinguaite, chemical analyses of the principal minerals, chemical estimates of the mode of the groundmass, and both chemical and micrometric modes of the pseudoleucite. The principal minerals are hedenbergitic acmite, a nepheline containing 2.3 per cent Fe₂O₃ and 7.9 per cent K₂O, and K-feldspar containing a little BaO and very little Na₂O. The micrometric mode of the pseudoleucite, in satisfactory agreement with the chemical mode, is nepheline 29.8 per cent, K-feldspar 66.2 per cent, acmite 3.0 per cent; the chemical mode of the groundmass is nepheline 26.8 per cent, K-feldspar 46.6 per cent, and acmite 26.7 per cent. A new analysis of a nepheline from the Bancroft area, made to test the analytical procedure, is also included.

Keywords

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