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Oneillite crystals
© Doug Merson
Na15CaMnFeZrNb(Si2573)(O,OH,HO)(OH,Cl)
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).
PHYSICAL CHARACTERISTICS:
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.
CLASSIFICATION:
Dana System
# 61.4.1.1
Strunz Classification
# VIII/E.17-5
REFERENCES:
CanMin 37:1295-1301 (1999)
DISTRIBUTION AND RARITY AT MONT SAINT-HILAIRE:
MSH
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