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.

Hardness

3-4

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrareLomonosovite Group family

Oneillite

Hardness: 3-4
Luster: Vitreous
Streak: White
Transparency: Translucent

No image

Is this oneillite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch oneillite with a known reference. Oneillite sits at Mohs 3-4 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Oneillite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Oneillite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: brown, yellow-brown.
5
Look at form & habit
Crystal system: triclinic. Typical habit: tabular crystals.

Often confused with

Oneillite vs. its common look-alikes — and how to tell them apart in the field.

mineral

Lomonosovite

Mohs 3-4

How to tell apart: Streak differs — Oneillite leaves white, Lomonosovite leaves yellowish brown.

How to tell apart: Luster reads vitreous on Oneillite and pearly on Murmanite.

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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: 3-4
Density: 3.16 g/cm³
Colors: Brown Yellow-brown
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Triclinic
Crystal habit: Tabular Crystals
Cleavage: Perfect On {001}
Rarity: Rare
Uses: Collector
Host rock: Agpaitic Pegmatites
Typical price: $50-300 per specimen

Where rockhounds find oneillite

Classic worldwide localities

Khibiny Massif, Russia
Lovozero Massif, Russia

Field-hunting tip

Look in agpaitic pegmatites country — that is 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?+

Mohs hardness is 3-4. It typically shows a vitreous luster. The streak is white. Common colors include brown, yellow-brown.

Where is oneillite found?+

Notable localities include Khibiny Massif, Russia; Lovozero Massif, Russia.

How much is oneillite worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like oneillite?+

Oneillite is most often confused with Lomonosovite, Murmanite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with oneillite?+

Oneillite commonly co-occurs with Nepheline, Aegirine, Microcline, Eudialyte. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does oneillite form in?+

Oneillite typically forms in agpaitic pegmatites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is oneillite used for?+

Oneillite is used in collector.

Find oneillite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.