Fergusonite-(Ce) is a rare radioactive rare-earth niobate mineral typically found in granitic pegmatites. It usually forms as small, brownish-black tetragonal prisms that are often metamict due to internal radiation damage. Collectors prize it for its unique chemistry and association with other rare earth minerals.
Is this fergusonite-(ce)?
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 fergusonite-(ce) with a known reference. Fergusonite-(Ce) sits at Mohs 5.5-6.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: reddish brown.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine.
- 4Match the color rangeCompare against the expected color range: dark red, black.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: irregular grains, prismatic.
Often confused with
Fergusonite-(Ce) vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Fergusonite-(Ce) leaves reddish brown, Fergusonite-(Y) leaves brown, yellow-brown, greenish gray; luster reads adamantine on Fergusonite-(Ce) and dull; vitreous to submetallic on fractures on Fergusonite-(Y).
How to tell apart: Streak differs, so Fergusonite-(Ce) leaves reddish brown, Euxenite-(Y) leaves yellowish, grayish, or reddish brown; luster reads adamantine on Fergusonite-(Ce) and brilliant submetallic, waxy to resinous on fractures on Euxenite-(Y).
Often found alongside fergusonite-(ce)
Minerals reported to co-occur with fergusonite-(ce). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CeNbO₄·0.3H₂O
- Mohs hardness
- 5.5-6.5
- Density
- 5.45-5.48 g/cm³
- Streak
- Reddish brown
- Luster
- Adamantine
- Transparency
- Semitransparent
- Crystal system
- Tetragonal
- Crystal habit
- Irregular grains, prismatic
- Cleavage
- Indistinct
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a carbonatite (Novopoltavsk massif, Russia); in magnesium-rich skarn of the outer granite contact zone of a carbonatite-derived dolomitic marble (Bayan Obo, China)
Where rockhounds find fergusonite-(ce)
Classic worldwide localities
- Granite Mountain, near Little Rock, Pulaski Co., Arkansas, USA
- Chernigovskaya zone, Novopoltavskii massif, Azov Sea area, Ukraine
- Eastern Bayan Obo Fe–Nb–RE deposit, 130 km north of Baotou, Inner Mongolia, China
Field-hunting tip
Where it forms: In a carbonatite (Novopoltavsk massif, Russia); in magnesium-rich skarn of the outer granite contact zone of a carbonatite-derived dolomitic marble (Bayan Obo, China). If you start seeing magnetite, phlogopite, graphite in float, you are in the right ground. Typical habit: irregular grains, prismatic. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify fergusonite-(ce)?+
Where is fergusonite-(ce) found?+
Is fergusonite-(ce) safe to handle?+
What rocks look like fergusonite-(ce)?+
What minerals are found with fergusonite-(ce)?+
What kind of rock does fergusonite-(ce) form in?+
What is fergusonite-(ce) used for?+
Find fergusonite-(ce) on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
