Gadolinite-(Y) is a rare silicate mineral primarily found in rare-element pegmatites. It typically occurs as dark, glassy prismatic crystals that often exhibit a brownish-green color when viewed in thin splinters under bright light.
Is this gadolinite-(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 gadolinite-(y) with a known reference. Gadolinite-(Y) sits at Mohs 6.5-7 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Gadolinite-(Y) leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Gadolinite-(Y) typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: black, brownish-black, greenish-black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, massive, granular.
Often confused with
Gadolinite-(Y) vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Gadolinite-(Y) leaves white, Allanite leaves gray; luster reads vitreous on Gadolinite-(Y) and submetallic on Allanite.
How to tell apart: Streak differs — Gadolinite-(Y) leaves white, Euxenite leaves yellowish, grayish, or reddish-brown; luster reads vitreous on Gadolinite-(Y) and submetallic, resinous, greasy on Euxenite.
Often found alongside gadolinite-(y)
Minerals reported to co-occur with gadolinite-(y). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Y₂Fe²⁺Be₂Si₂O₁₀
- Mohs hardness
- 6.5-7
- Density
- 4.0-4.5 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic Crystals, Massive, Granular
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Source of Rare Earth Elements
- Host rock
- Granite Pegmatites
- Typical price
- $20-200 thumbnail
Where rockhounds find gadolinite-(y)
Classic worldwide localities
- Sweden
- Norway
- USA
- Madagascar
- Japan
Field-hunting tip
Look in granite pegmatites country — that is the host setting where gadolinite-(y) typically forms. If you start seeing microcline, zircon, fluorite in float, you are in the right ground. Field specimens usually show a prismatic crystals, massive, granular habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify gadolinite-(y)?+
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What rocks look like gadolinite-(y)?+
What minerals are found with gadolinite-(y)?+
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Find gadolinite-(y) on the map
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