© Doug Merson
Oneillite is one of three new members of the eudialyte group from Mont Saint-Hilaire. It was first collected by Quintin Wight in 1994 at a contact between a vein of fine-grained albite and the host rock, nepheline syenite.
It is very rare. It is brittle and does not fluoresce. There has been only one specimen collected containing ~ 100 mgs of oneillite.
Johnston O’Neil was the first to describe the geology of Mont Saint-Hilaire and first to report the presence of peralkaline minerals at this locality (O’Neill 1914).
Color is yellowish brown.
Luster is vitreous.
Diaphaneity is transparent to translucent.
Crystal System is trigonal;3.
Crystal Habits include anhedral grains to 2mm.
Cleavage is not apparent.
Fracture is uneven.
Hardness is 5 – 6.
Specific Gravity is approximately 3.20 g/cm
Streak is white.
Associated Minerals include aegirine, albite, pyrite and sodalite.
Distinguishing Features: Crystal habit and color.
Origin: Named to honor of Johnston O’Neill (1886-1966), a geologist
with the Geological Survey of Canada in 1998.
CanMin 37:1295-1301 (1999)
DISTRIBUTION AND RARITY AT MONT SAINT-HILAIRE: