Home > Mineral Abstracts > CanMin Vol. 24, pp. 449-453 (1986)




Vol. 24, pp. 449-453 (1986)



Hochelagaite,
a new calcium-niobium oxide mineral
from Montreal, Quebec


John L. Jambor
CANMET, 555 Booth Street, Ottawa, Ontario K1A 0G1


Ann P. Sabina, Andrew C. Roberts and Maurizio Bonardi
Geological Survey of Canada,
601 Booth Street, Ottawa, Ontario K1A 0E8



D'Alton R. Owens
CANMET, 555 Booth Stree, Ottawa, Ontario K1A 0G1


B. Darko Sturman
Department of Mineralogy and Geology,
Royal Ontario Museum, Toronto, Ontario, M5S 2C6


ABSTRACT

     The new mineral hochelagaite occurs as white globules, 150 mm across, in vugs of a dawsonite-bearing sill in the Francon limestone quarry, Montreal, Quebec. The globules consist predominantly of radiating bladed crystals with a vitreous lustre, white streak, hardness 4. Optically, we measure na 1.72(1), nb 1.81 (1), ng 1.82(1), (-)2V
35(5)o; Z is parallel to the elongation (c) and a (b) is perpendicular to the sides. Microprobe analyses of four globules gave, in wt.%:


CaO - 6.3 - 7.7
SrO - 0.0 - 1.2
Na2O - 0.0 - 1.3
Nb2O5 - 71.7 - 78.3

TiO2 - 1.2 - 1.5
Al2O3 - 0.0 - 0.8
SiO2 - 0.4 - 1.5
H2O - 10.3 - 18.9
(H2O by difference)



         The results correspond to (Ca,Na,Sr)(Nb,Ti,Si,Al)4O11 · nH2O, where n is probably 8. Indexing of the X-ray powder pattern gave a 19.88(1),
b 12.83(1), c 6.44(1) Å, b 93.20(3)o. Measured densities range from 2.85 to 2.94 g/cm3, and calculated values range from 2.82 to 2.88 g/cm3 assuming 8 H2O and Z = 4. The strongest lines of the X-ray are:


10.0(10)
5.39 (5)
4.96 (5)

3.208(7)
3.115(8)
2.799(4)


     Many of the properties of hochelagaite are similar to those of franconite; on heating, however, hochelagaite decomposes to CaNb4O11, whereas franconite goes to Na2Nb4O11. The new name is derived from Hochelaga, the original name for Montreal. UK-50 from Mont St-Hilaire is hochelagaite.

Keywords:  hochelagaite, new mineral species, Ca-Nb oxide hydrate, Francon quarry, Montreal, Quebec, UK-50, Mont St-Hilaire, Quebec.


© 1986  The Canadian Mineralogist