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Armstrongite from the Strange Lake Alkalic Complex, on the Quebec – Labrador Boundary, Canada

Published online by Cambridge University Press:  28 October 2013

John L. Jambor
Affiliation:
CANMET, 555 Booth Street, Ottawa, Ontario, CanadaK1A OG1
Andrew C. Roberts
Affiliation:
Geological Survey of Canada, 601 Booth Street, Ottawa, OntarioCanadaK1A OE8
Joel D. Grice
Affiliation:
Mineral Sciences Division, National Museum of Natural Sciences, Ottawa, Ontario, CanadaK1A OM8

Abstract

Tabular untwinned crystals of colorless transparent armstrongite from the Strange Lake Alkalic Complex, on the Quebec – Labrador boundary, Canada are monoclinic, space group choices I2/m, I2, Im (diffraction aspect I*/*), with refined unit-cell parameters a = 13.599 (9), b = 14.114(9), c = 7.833 (4) Å, β = 103.41 (5)°, V = 1462.4 (±3.0) Å3. a:b:c = 0.9635:1:0.5550, Z = 4 and D(x) = 2.696 g/cm3. A fully indexed X-ray powder pattern is presented. Averaged electron-microprobe analyses suggest a theoretical formula of CaZrSi6O15 · 3 H2O. The Strange Lake armstrongite is biaxial negative, α = 1.567 (1), β = 1.576 (1), γ = 1.577 (1), 2V (meas.) = 39 (1)°, 2V (calc.) = 37°, Z∥b, X Λc = +4°, with no absorption and weak dispersion r < v.

Type
Research Article
Copyright
Copyright © Cambridge University Press 1987

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