Home > Mineral Abstracts > CanMin Vol. 29, pp. 359-362 (1991)




Vol. 29, pp. 359-362 (1991)



Silinaite, a new sodium lithium silicate hydrate mineral
from Mont Saint-Hilaire, Quebec


George Y. Chao
Ottawa-Carleton Geoscience Centre, Department of Earth Sciences,
Carleton University, Ottawa , Ontario K1S 5B6



Joel D. Grice and Robert A. Gault
Mineral Sciences Section, Earth Sciences Division,
Canadian Museum of Nature,
Ottawa , Ontario K1P 6P4


ABSTRACT

     Silinaite, ideally NaLiSi2O5 · 2H2O, is a new mineral species from the Poudrette quarry, Mont Saint-Hilaire, Quebec.  It occurs as clear tabular crystals up to 2 mm, fibrous cluster, poorly formed prismatic crystals, and chalky to earthy or pwdery patches in sodalite syenite xenoliths in the nepheline syenite.   It is associated with many rare species such as erdite, kogarkoite, tugtupite, vitusite-(C), makatite, thalcusite, chkalovite, sazhinite-(Ce), sidorenkite, revdite, rasvumite, natrophosphate and many unidentified minerals.  The mineral is brittle, colorless to white with a white streak, opaque to translucent or transparent with vitreous to earthy luster.  Cleavages {001} perfect, {010} good and {110} distinct; fracture conchoidal; Mohs hardness 4.5; D(meas.) 2.24(1), D(calc.) 2.22 and 2.23 g/cm3; non-fluorescent in ultraviolet light.  g/cm3; non-fluorescent in ultraviolet light.  Optically biaxial positive, a 1.515(1), b 1.516(1), g 1.518(1), 2V (meas.) 64(1)°, 2V(calc.) 71° (g 589nm).  Orientation:  X = b, Y & c = 16° in the acute b angle.  Nonpleochroic; strong r > v, inclined.  Silinaite is monoclinic, A2/n, a 5.061(1), b 8.334(2), c 14.383(3) Å, b 96.67(2)°, Z = 4.  The strongest eight X-ray Gandolfi diffraction lines [d in Å (I)(hkl)] are:

7.14 (100)(011,002)
4.24 (80)(111)
4.14 (100)(013)
4.02 (80)(111)

2.847 (100)(122)
2.698 (50)(015)
1.610 (40)(311,137,240)
1.557 (40)(322)


     The ideal chemical formula is derived from a crystal-structure analysis.  Electron-microprobe analyses gave:

SiO2 58.54, 58.72
Al2O3 0.01, 0.00
CaO 0.14, 0.42

Na2O 14.96, 13.66
Li2O 7.28, 7.25 (calc.)
H2O 17.56, 17.47 (calc.)


     Sums 98.49, 97.52 wt.%, corresponding to (Na0.99Ca0.01)LiSi2.00O5 · 2H2O.  The name is derived from the composition.

Keywords:  silinaite, sodium lithium silicate hydrate, new mineral species, Mont Saint-Hilaire, Quebec, occurrence, properties, X-ray data, chemical composition.



© 1991  The Canadian Mineralogist