Home > Mineral Abstracts > CanMin Vol. 38, pp. 1457-1466 (2000)

Vol. 38, pp. 1457-1466 (2000)

Adamsite-(Y), a new sodium-yttrium carbonate mineral species from
Mont Saint-Hilaire, Québec

Joel D. Grice* and Robert A. Gault
Research Division, Canadian Museum of Nature,
P.O. Box 3443, Station D, Ottawa, Ontario K1P 6P4, Canada

Andrew C. Roberts
Geological Survey of Canada, 601 Booth Street,
Ottawa, Ontario K1A 0E8, Canada

Mark A. Cooper
Department of Geological Sciences, University of Manitoba,
Winnipeg, Manitoba R3T 2N2, Canada


     Adamsite-(Y), ideally NaY(CO3)2 · 6H2O, is a newly identified mineral from the Poudrette quarry, Mont Saint-Hilaire, Quebec. It occurs as groups of colorless to white and pale pink, rarely pale purple, flat, acicular to fibrous crystals. These crystals are up to 2.5cm in length and form spherical aggregates. Associated minerals include aegirine, albite, analcime, ancylite-(Ce), calcite, catapleiite, dawsonite, donnayite-(Y), elpidite, epididymite, eudialyte, eudidymite, fluorite, franconite, gaidonnayite, galena, genthelvite, gmelinite, gonnardite, horv├íthite-(Y), kupletskite, leifite, microcline, molybdenite, narsarsukite, natrolite, nenadkevichite, petersenite-(Ce), polylithionite, pyrochlore, quartz, rhodochrosite, rutile, sabinaite, sérandite, siderite, sphalerite, thomasclarkite-(Y), zircon and an unidentified Na-REE carbonate (UK 91). The transparent to translucent mineral has a vitreous to pearly luster and a white streak. It is soft (Mohs hardness 3) and brittle with perfect {001} and good {100} and {010} cleavages. Adamsite-(Y) is biaxial positive, a = 1.480(4), b = 1.498(2), g = 1.571(4), 2Vmeas.=53(3)°, 2Vcalc.=55° and is nonpleochroic. Optical orientation: X=[001], Y=b, Z a=14° (in b obtuse). It is triclinic, space group P1, with unit-cell parameters refined from powder data: a 6.262(2), b 13.047(6), c 13.220(5) Å, a 91.17(4), b 103.70(4), g 89.99(4)°, V 1049.1(5) Å3 and Z = 4.

     The strongest six X-ray powder-diffraction lines [d in Å (I)(hkl)] are:



     Electron-microprobe and thermogravimetric analyses, supported by crystal-structure analysis and infrared absorption spectroscopy, yield:

Na2O - 8.64
CaO - 0.05
Y2O3 - 22.88
Ce2O3 - 0.37
Nd2O3 - 1.41
Sm2O3 - 1.02
Gd2O3 - 1.92
Tb2O3 - 0.56
Dy2O3 - 3.28
Ho2O3 - 0.90
Er2O3 - 2.83
Tm2O3 - 0.27
Yb2O3 - 1.04
CO2 - 25.10
H2O - 29.90
Total 100.17 wt.%

     The empirical formula, based on 12 oxygen atoms, is:


Tb0.01Tm0.01)S0.99 C2.04H11.87O12.

     The calculated density (from the empirical formula) is 2.27 g/cm3, and the measured density is 2.27(2) g/cm3. The structure has been refined to R = 0.046. The structure is layered, with two different carbonate groups, one parallel and one perpendicular to the layering. Slabs of [NaY(CO3)] are separated by [H2O)] layers. Adjacent [H2O)] layers are only H-bonded together, which gives rise to the perfect {001} cleavage. The mineral is named after Frank Dawson Adams (1859-1942), geologist and professor at McGill University, Montreal.

Keywords: adamsite-(Y), new mineral species, sodium yttrium dicarbonate hexahydrate, crystal structure, Mont Saint-Hilaire, Quebec, Canada.

     * E-mail address: jgrice@mus-nature.ca

© 2000  The Canadian Mineralogist