Oneillite is a complex silicate mineral primarily occurring in alkaline igneous complexes. It forms as thin, brittle tabular crystals within pegmatite pockets, typically found alongside other rare zirconium and titanium minerals.
Is this oneillite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch oneillite with a known reference. Oneillite sits at Mohs 5-6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Oneillite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Oneillite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: brown, yellow-brown.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: tabular crystals.
Often confused with
Oneillite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Oneillite is noticeably harder (Mohs 5-6 vs. 3-4); streak differs, so Oneillite leaves white, Lomonosovite leaves light rose-cinnamon.
How to tell apart: Oneillite is noticeably harder (Mohs 5-6 vs. 2-3); luster reads vitreous on Oneillite and pearly on Murmanite.
Often found alongside oneillite
Minerals reported to co-occur with oneillite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₁₅Ca₃Mn₃Fe₃Zr₃Nb(Si₂O₇)₃(PO₄)₄O₂F₂
- Mohs hardness
- 5-6
- Density
- 3.16 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Hexagonal
- Crystal habit
- Tabular Crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Agpaitic Pegmatites
Where rockhounds find oneillite
Classic worldwide localities
- Poudrette quarry, Rouville County, Quebec, Canada
Field-hunting tip
Look in agpaitic pegmatites country, the host setting where oneillite typically forms. If you start seeing nepheline, aegirine, microcline in float, you are in the right ground. Field specimens usually show a tabular crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify oneillite?+
Where is oneillite found?+
What rocks look like oneillite?+
What minerals are found with oneillite?+
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What is oneillite used for?+
Find oneillite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
