CALCIOBURBANKITE, Na3(Ca,REE,Sr)3(CO3)5, A NEW MINERAL SPECIES FROM MONT
SAINT-HILAIRE, QUEBEC, AND ITS RELATIONSHIP TO THE BURBANKITE GROUP OF MINERALS
JERRY VAN VELTHUIZEN, ROBERT A. GAULT & JOEL D. GRICE
Mineral Sciences Section, Research Division, Canadian Museum of Nature, P.O. Box 3443, Station "D",
Ottawa, Ontario K1P 6P4
Abstract
Calcioburbankite, ideally Na3(Ca,REE,Sr)3(CO3)5, is a new mineral species found at Mont Saint- Hilaire,
Quebec. It is the Ca-analogue of burbankite, (Na,Ca)3(Sr,Ba,Ce)3(CO3)5, and of khanneshite,
(Na,Ca)3(Ba,Sr,Ce,Ca)3(CO3)5. All data were collected from a single, subhedral, deep orange coloured,
prismatic crystal 2 × 1.8 × 2 cm in size. Associated minerals include ancylite-(Ce), calcite, a
chlorite-group mineral, donnayite-(Y), fluorapatite, natrolite, pyrite, rhodochrosite and rutile. It
is elongate parallel to [001], with {100} dominant. It has a conchoidal fracture, a
vitreous luster and indistinct {100} cleavage. The mineral is soft, Mohs hardness 3 to 4,
gives a white streak and is brittle. Optically, the mineral is uniaxial negative, 1.636(1), 1.631(1) ( 589 nm).
It is transluscent, nonpleochroic and nonfluorescent. Combined X-ray powder-diffraction and precession studies
show that the mineral is hexagonal, possible space-groups P63mc, P63mmc or P62c. The unit-cell data,
refined from the powder data, give a 10.447(3) c 6.318(3) Å, V 597.23(2) Å3, a:c 0.6048(4). The strongest eight
reflections determined from the powder data [d in Å(I)(hkl)] are 2.601(10)(220), 2.130(6)(401),
3.01(5)(300,211), 5.20(4)(110), 3.68(3)(201), 1.649(3)(421), 4.54(2)(200) and 9.07(2)(100). Electron-microprobe results
gave Na2O 15.17, CaO 11.81, BaO 0.46, SrO 7.65, La2O3 9.30, Ce2O3 14.38, Pr2O3 1.26, Nd2O3 3.76, Sm2O3 0.48
and CO2 (calculated according to stoichiometry) 35.13, total 99.40 wt.%. The empirical formula (based on O = 15)
is Na3.07(Ca1.32Ce0.55Sr0.46La0.36Nd0.14Pr0.05Sm0.02Ba0.02) 2.92(CO3)5, for Z = 2, Dcalc 3.46 and
Dmeas 3.45(3) g/cm3. The mineral formed late in the paragenesis, possibly in a vent. The name
designates its calcium-dominant position within hexagonal members of the burbankite group of minerals.
The physical data of calcioburbankite are compared to those of other members of the burbankite group.
Keywords: calcioburbankite, Ca-analogue, burbankite group, new mineral species,
carbonate, Mont Saint-Hilaire, Quebec.