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Re-examination of the mineral tuhualite

Published online by Cambridge University Press:  14 March 2018

C. Osborne Hutton
C. Osborne Hutton*
Affiliation:
Stanford University, Palo Alto, California, U.S.A.
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Summary

X-ray study of tuhualite from Mayor Island, New Zealand, has shown it to be orthorhombic, space-group either . Unit-cell dimensions are a = 14·31 Å, b = 17·28 Å., c = 10·11 Å., and a : b : c = 0·828 : 1 : 0·585. Goniometric measurements give a : b : c = 0·8243 : 1 : 0·5658. a{100} dominant with forms s{011}, p{021}, c{001}, b{010}, n{101}, m{110}, q{111}. Crystals with b{010} dominant are rare. Three good cleavages, a (100), b (010), c (001). α = 1·608, β = 1·612, γ = 1·621; γ-α = 0·013. , positive; β = b, γ = c, α = colourless to pale lavender, β = violet, lavender, γ = intense purplish-blue; γ > β > α. Sp. gr. 2·89 (measured), 2·86 (calculated).

An analysis of carefully purified material leads to the possible formula:

H9(Na,K,Mn)12Fe″6(Al,Fe‴,Mg,Ti)9[Si8O8]15.

Details of alteration phenomena and associated minerals are given. Occurrence is held to result by crystallization from magma quite impoverished in lime due to early fractionation of aegirine-hedenbergite, and perhaps aegirine-augite, in the intratelluric stage.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 31 , Issue 232 , March 1956 , pp. 96 - 106
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1956

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References

Bartrum, (J. A.), 1926. New Zealand Journ. Sci. Techn., vol. 8, p. 214.Google Scholar
Marshall, (P.), 1932. Ibid., vol. 13, p. 198 [M.A. 5-294].Google Scholar
Marshall, (P.), 1936A. Trans. Roy. Soc. New Zealand, vol. 66, p. 337 [M.A. 7-45].Google Scholar
Marshall, (P.), 1936B. Ibid., vol. 66, p. 330 [M.A. 6-536].Google Scholar
Wolff, (F. von), 1904. Centr. Min., p. 208.Google Scholar