Fergusonite-(Y) is a rare earth niobate mineral typically found as prismatic crystals in granite pegmatites. It is almost always found in a metamict state, where radioactive decay has disrupted its original crystal lattice, resulting in a dark, glassy appearance.
Is this fergusonite-(y)?
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-(y) with a known reference. Fergusonite-(Y) 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. Fergusonite-(Y) leaves a pale yellow streak.
- 3Read the lusterHold the specimen under a strong light. Fergusonite-(Y) typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: black, brownish-black, yellowish-brown, greenish-gray.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: prismatic crystals, pyramidally terminated, often metamict.
Often confused with
Fergusonite-(Y) vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Fergusonite-(Y) leaves pale yellow, Euxenite leaves yellowish, grayish, or reddish-brown; luster reads vitreous on Fergusonite-(Y) and submetallic, resinous, greasy on Euxenite.
How to tell apart: Streak differs — Fergusonite-(Y) leaves pale yellow, Columbium Ore leaves dark red to black; luster reads vitreous on Fergusonite-(Y) and submetallic on Columbium Ore.
Often found alongside fergusonite-(y)
Minerals reported to co-occur with fergusonite-(y). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- YNbO₄
- Mohs hardness
- 5.5-6.5
- Density
- 5.6-5.8 g/cm³
- Streak
- Pale Yellow
- Luster
- Vitreous
- Transparency
- Opaque
- Crystal system
- Tetragonal
- Crystal habit
- Prismatic Crystals, Pyramidally Terminated, Often Metamict
- Cleavage
- Indistinct
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Granite Pegmatites
- Typical price
- $20-150 per specimen depending on size and crystal quality
Where rockhounds find fergusonite-(y)
Classic worldwide localities
- Ytterby, Sweden
- Hittero, Norway
- Madagascar
- Greenland
- USA (Colorado)
Field-hunting tip
Look in granite pegmatites country — that is the host setting where fergusonite-(y) typically forms. If you start seeing zircon, monazite, allanite in float, you are in the right ground. Field specimens usually show a prismatic crystals, pyramidally terminated, often metamict habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify fergusonite-(y)?+
Where is fergusonite-(y) found?+
How much is fergusonite-(y) worth?+
Is fergusonite-(y) safe to handle?+
What rocks look like fergusonite-(y)?+
What minerals are found with fergusonite-(y)?+
What kind of rock does fergusonite-(y) form in?+
What is fergusonite-(y) used for?+
Find fergusonite-(y) on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
