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Emeleusite: a new LiNaFeIII silicate from south Greenland

Published online by Cambridge University Press:  05 July 2018

B. G. J. Upton ,
P. G. Hill ,
O. Johnsen  and
O. V. Petersen
B. G. J. Upton
Affiliation:
Department of Geology, Edinburgh EH9 3JW
P. G. Hill
Affiliation:
Department of Geology, Edinburgh EH9 3JW
O. Johnsen
Affiliation:
Geological Museum, University of Copenhagen, DK-1350 Copenhagen K
O. V. Petersen
Affiliation:
Geological Museum, University of Copenhagen, DK-1350 Copenhagen K
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Summary

Emeleusite (Li2Na4Fe2IIISi12O30) is an orthorhombic (pseudohexagonal) mineral occurring as euhedra within a facies of a peralkaline trachyte dyke. The composition is: SiO2 70·75; TiO2 0·55; ZrO2 0·10; Al2O3 1·34; Fe2O3 12·13; MgO 0·10; MnO 0·03; Na2O 11·98; Li2O 2·78:99·76. The density is 2·775 g/cm3 (calculated) and 2·76(7) g/cm3 (determined); hardness 5–6. It is colourless, transparent, and has a glassy lustre. Emeleusite is biaxial negative with 2Va, varying from near-zero to c. 30° r » v. The refractive indices are α 1·596; β 1·597; y 1·597; with α ∥ b; β ∥ a; y ∥ c. Emeleusite can occur as interpenetration triplets with {110} as twin planes. The space group is Acam or Aba2 with a = 10·073±0·002 Å; b = 17·350±0·005 Å and c = 14·010±0·005 Å. Z = 4. Prominent powder diffraction lines are 7·001(5) 002, 4·352(10) 220, 040, 3·501(7) 004, 3·209(8) 311, and 3·090(7) 124. While the structure is as yet unknown it is suggested that it is an orthorhombic associate of the milarite group.

Type
Research Article
Information
Mineralogical Magazine , Volume 42 , Issue 321 , March 1978 , pp. 31 - 34
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1978

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References

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