Datolite, a member of the gadolinite group, is rare at Mont Saint-Hilaire. Color varies from pale yellow to greenish-yellow and white. Luster is vitreous and dull on spheres. Crystal Habits include excellent short prismatic crystals to 20mm and spheres with radiating internal structure to 1mm. Cleavage none observed.
Fracture is uneven to conchoidal.
Streak is white. Associated Minerals include albite, amphibole group, apophyllite series, chlorite group, fluorite, hibschite and pectolite. Color and lack of cleavage.