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Emeleusite: a new LiNaFeIII silicate from south Greenland

  • B. G. J. Upton (a1), P. G. Hill (a1), O. Johnsen (a2) and O. V. Petersen (a2)

Summary

Emeleusite (Li2Na4Fe2 IIISi12O30) 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 2V a , varying from near-zero to c. 30° r » v. The refractive indices are α 1·596; β 1·597; y 1·597; with αb; βa; yc. 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.

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References

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Dunn, (P. J.), Rouse, (R. C.), Cannon, (B.), and Nelen, (J. A.), 1977. Zektzerite: A new lithium sodium zirconium silicate related to tuhualite and the osumilite group. Am. Mineral. 62, 416.
Hutton, (C. O.), 1956. Re-examination of the mineral tuhualite. Mineral. Mag. 31, 96-106.
Merlino, (S.), 1969. Tuhualite crystal structure. Science, 166, 1399-1401.
Micheelsen, (H.), 1957. An immersion method for exact determination of refractive indices. The glass method. Meddr. Dansk geol. Foren. 13, 177-9.
Sweatman, (T. R.) and Long, (J. V. P.), 1969. Quantita-tive electron-probe microanalysis of rock-forming minerals. J. Petrol. 10, 332-79.
Upton, (B. G. J.), Macdonald, (R.), Hill, (P. G.), Jefferies, (B.), and Ford, (C. E.), 1976. Narsarsukite: a new occurrence in peralkaline trachyte, south Greenland. Mineral. Mag. 40, 737-46.

Emeleusite: a new LiNaFeIII silicate from south Greenland

  • B. G. J. Upton (a1), P. G. Hill (a1), O. Johnsen (a2) and O. V. Petersen (a2)

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