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Macaulayite, a new mineral from North-East Scotland

Published online by Cambridge University Press:  05 July 2018

M. J. Wilson ,
J. D. Russell ,
J. M. Tait ,
D. R. Clark  and
A. R. Fraser
M. J. Wilson
Affiliation:
The Macaulay Institute for Soil Research, Craigiebuckler, Aberdeen, Scotland
J. D. Russell
Affiliation:
The Macaulay Institute for Soil Research, Craigiebuckler, Aberdeen, Scotland
J. M. Tait
Affiliation:
The Macaulay Institute for Soil Research, Craigiebuckler, Aberdeen, Scotland
D. R. Clark
Affiliation:
The Macaulay Institute for Soil Research, Craigiebuckler, Aberdeen, Scotland
A. R. Fraser
Affiliation:
The Macaulay Institute for Soil Research, Craigiebuckler, Aberdeen, Scotland
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Abstract

Macaulayite was found by the late I. Stephen (Soil Science Department, University of Aberdeen) in an outcrop of reddened, deeply weathered granite, near Inverurie, Aberdeenshire. It is blood red in colour, very fine-grained, and has refractive indices greater than 1.734. Its calculated density is 4.41 g/cm3. The mean of fourteen electron microprobe analyses in the anhydrous form is Fe2O3 84.67, Al2O3 4.01, SiO2 11.32%. With thermogravimetric data this leads to a formula of (Al3.38)Si7.95O86(OH)4; the ideal formula is Si4O43(OH)2. The cell indexes as C-centred monoclinic with a 5.038, b 8.726, c 36.342Å, β 92°. The strongest X-ray lines are 36.6 (vs), 18.16 (vs), 3.700 (25), 2.720 (35), 2.533 (100), 2.214 (20), and 1.420 (35). Macaulayite has a layer structure, thought to consist of a double hematite unit terminated on both sides by silicate sheets and with water between these sheets. The infra-red spectrum includes absorption bands at 3597, 1052, 1033, and 858 cm−1, arising from the hydroxysilicate component of the mineral and at 647, 520, 438, 400, 304, and 227 cm−1 corresponding to the platy hematite unit. The mineral is named for the Macaulay Institute for Soil Research and the name was approved by the Commission on New Minerals and Mineral Names of the International Mineralogical Association prior to publication.

Type
Research Article
Information
Mineralogical Magazine , Volume 48 , Issue 346 , March 1984 , pp. 127 - 129
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1984

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References

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