Abstract

The new mineral species franconite occurs as white 150-mu m globules on crystals of weloganite, calcite and quartz in vugs in a dawsonite-bearing sill in the Francon limestone quarry, Montreal, Quebec. The globules consist of bladed crystals, which show vitreous lustre, white streak, basal parting and have nalpha 1.72(1), nbeta 1.78(1), ngamma 1.79(1), (-)2V 35(5) degrees ; Z is parallel to the elongation, and X is perpendicular to the blades. The average composition deduced from chemical analysis of five globules corresponds to (Na (sub 1.69) Ca (sub 0.12) Sr (sub 0.01) ) (sub Epsilon 1.82) (Nb (sub 3.81) Ti (sub 0.09) Al (sub 0.01) Si (sub 0.09) ) (sub Epsilon 4.00) O (sub 10.88) .9H 2 O. Indexing of the X-ray powder pattern gave the cell a 22.22(1), b 12.857(5), c 6.359(4) Aa, beta 92.24(6) degrees , which for the average composition gives D calc 2.71 g/cm 3 for Z = 4; D meas = 2.72(1) g/cm 3 . Heating of franconite to 500 degrees C produces Na 2 Nb 4 O 11 .--Modified journal abstract.

First Page Preview

First page PDF preview
You do not currently have access to this article.