Allanite-(La) is a member of the epidote group, characterized by high lanthanum content and structural thorium. It is typically found as dark, opaque, prismatic crystals that often exhibit a pitch-like luster when fresh, though it is frequently found in a metamict state due to its radioactivity.
Is this allanite-(la)?
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-(la) with a known reference. Allanite-(La) 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-(La) leaves a brown streak.
- 3Read the lusterHold the specimen under a strong light. Allanite-(La) typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: black, brown, reddish-brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, tabular, massive, granular.
Often confused with
Allanite-(La) vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Allanite-(La) leaves brown, Epidote leaves white.
How to tell apart: Streak differs, so Allanite-(La) leaves brown, Allanite-(Ce) leaves gray; luster reads vitreous on Allanite-(La) and submetallic on Allanite-(Ce).
How to tell apart: Streak differs, so Allanite-(La) leaves brown, Allanite leaves gray; luster reads vitreous on Allanite-(La) and submetallic on Allanite.
Often found alongside allanite-(la)
Minerals reported to co-occur with allanite-(la). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (La,Ca,Ce,Th)₂(Al,Fe³⁺,Fe²⁺)₃(SiO₄)₃(OH)
- Mohs hardness
- 5.5-6
- Density
- 3.5-4.2 g/cm³
- Colors
- Streak
- Brown
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic Crystals, Tabular, Massive, Granular
- Cleavage
- Imperfect On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Granite Pegmatites, Syenites, Contact Metamorphosed Limestones
Where rockhounds find allanite-(la)
Classic worldwide localities
- Buca della Vena Mine, Lucca Province, Tuscany, Italy
Field-hunting tip
Look in granite pegmatites, syenites, contact metamorphosed limestones country, the host setting where allanite-(la) typically forms. If you start seeing feldspar, quartz, biotite in float, you are in the right ground. Field specimens usually show a prismatic crystals, tabular, massive, granular habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify allanite-(la)?+
Where is allanite-(la) found?+
Is allanite-(la) safe to handle?+
What rocks look like allanite-(la)?+
What minerals are found with allanite-(la)?+
What kind of rock does allanite-(la) form in?+
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Find allanite-(la) on the map
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