Allanite-(Y) is a rare-earth-bearing member of the epidote group typically found in granitic pegmatites. It often displays a distinct black or brownish-black color and submetallic luster, and it is almost always metamict, meaning its crystal structure has been partially destroyed by radioactive decay.
Is this allanite-(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 allanite-(y) with a known reference. Allanite-(Y) sits at Mohs 5.5-6 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Allanite-(Y) leaves a gray streak.
- 3Read the lusterHold the specimen under a strong light. Allanite-(Y) typically shows a submetallic luster.
- 4Match the color rangeCompare against the expected color range: black, brown, reddish-brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, massive, granular.
Often confused with
Allanite-(Y) vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Allanite-(Y) leaves gray, Epidote leaves white; luster reads submetallic on Allanite-(Y) and vitreous on Epidote.
How to tell apart: Streak differs — Allanite-(Y) leaves gray, Allanite-(Ce) leaves greyish-white.
Often found alongside allanite-(y)
Minerals reported to co-occur with allanite-(y). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Y,Ca,Ce)₂(Al,Fe³⁺,Fe²⁺)₃(SiO₄)₃(OH)
- Mohs hardness
- 5.5-6
- Density
- 3.5-4.2 g/cm³
- Colors
- Streak
- Gray
- Luster
- Submetallic
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic Crystals, Massive, Granular
- Cleavage
- Indistinct
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Granite Pegmatites, Syenites
- Typical price
- $20-150 per specimen
Where rockhounds find allanite-(y)
Classic worldwide localities
- Sweden
- Norway
- USA
- Russia
- Madagascar
Field-hunting tip
Look in granite pegmatites, syenites country — that is the host setting where allanite-(y) typically forms. If you start seeing quartz, microcline, biotite 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 allanite-(y)?+
Where is allanite-(y) found?+
How much is allanite-(y) worth?+
Is allanite-(y) safe to handle?+
What rocks look like allanite-(y)?+
What minerals are found with allanite-(y)?+
What kind of rock does allanite-(y) form in?+
What is allanite-(y) used for?+
Find allanite-(y) on the map
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