Zirconolite is a rare accessory mineral typically found in silica-undersaturated igneous rocks like carbonatites and alkaline syenites. Collectors prize it for its high density and status as a primary mineral host for radioactive elements like thorium and uranium in geological systems.
Is this zirconolite?
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 zirconolite with a known reference. Zirconolite sits at Mohs 6.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brownish yellow to dark brown.
- 3Read the lusterHold the specimen under a strong light. Luster: submetallic; adamantine to greasy.
- 4Match the color rangeCompare against the expected color range: black, brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: massive, prismatic, striated.
Often confused with
Zirconolite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Zircon is the harder of the two (Mohs 7.5 vs. 6.5); streak differs, so Zirconolite leaves brownish yellow to dark brown, Zircon leaves white; luster reads submetallic; adamantine to greasy on Zirconolite and vitreous to adamantine; greasy when metamict on Zircon.
How to tell apart: Streak differs, so Zirconolite leaves brownish yellow to dark brown, Baddeleyite leaves white to brownish white; luster reads submetallic; adamantine to greasy on Zirconolite and greasy to vitreous; nearly submetallic in black crystals on Baddeleyite.
How to tell apart: Zirconolite is noticeably harder (Mohs 6.5 vs. 5-5.5); streak differs, so Zirconolite leaves brownish yellow to dark brown, Pyrochlore leaves brown; luster reads submetallic; adamantine to greasy on Zirconolite and vitreous to resinous on Pyrochlore.
Often found alongside zirconolite
Minerals reported to co-occur with zirconolite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Ca,Y)Zr(Ti,Mg,Al)₂O₇
- Mohs hardness
- 6.5
- Density
- 4.017-4.237 g/cm³
- Streak
- Brownish yellow to dark brown
- Luster
- Submetallic; adamantine to greasy
- Transparency
- Opaque, transparent in thin fragments
- Crystal system
- Monoclinic
- Crystal habit
- Massive, prismatic, striated
- Cleavage
- {100}, {010} in traces
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- In alkaline rocks, as carbonatites, kimberlites, syenites, sanidinites; more rarely in ultramafic rocks; in felsic pegmatite in gabbro; a detrital mineral
Where rockhounds find zirconolite
Classic worldwide localities
- Afrikanda pyroxenite massif, Kola Peninsula, Russia
- Fredriksvärn, and Agnes Sandefjord, Vestfold, Norway
- Kaiserstuhl carbonatite, Baden-Württemberg, Germany
- Monte di Procida, Campi Flegrei, Campania, Italy
- Laouni intrusive, 250 km south of Tamanrasset, Algeria
- Walaweduwa, Sri Lanka
Field-hunting tip
Where it forms: In alkaline rocks, as carbonatites, kimberlites, syenites, sanidinites; more rarely in ultramafic rocks; in felsic pegmatite in gabbro; a detrital mineral. If you start seeing apatite, clinohumite, phlogopite in float, you are in the right ground. Typical habit: massive, prismatic, striated. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify zirconolite?+
Where is zirconolite found?+
Is zirconolite safe to handle?+
What rocks look like zirconolite?+
What minerals are found with zirconolite?+
What kind of rock does zirconolite form in?+
What is zirconolite used for?+
Find zirconolite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
