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 6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brown.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: black, brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic.
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 grayish white.
How to tell apart: Streak differs, so Allanite-(La) leaves brown, Allanite-(Ce) leaves gray.
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
- CaLaFeAl₂(Si₂O₇)(SiO₄)O(OH)
- Mohs hardness
- 6
- Density
- 3.93 g/cm³
- Streak
- Brown
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic
- Cleavage
- Imperfect on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In barite veins that cut a dolomitic metamorphosed limestone
Where rockhounds find allanite-(la)
Classic worldwide localities
- Castello zone of the Buca della Vena mine, near Stazzema, Apuan Alps, Tuscany, Italy
Field-hunting tip
Where it forms: In barite veins that cut a dolomitic metamorphosed limestone. If you start seeing calcite, barite in float, you are in the right ground. Typical habit: prismatic. 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?+
What is allanite-(la) used for?+
Find allanite-(la) on the map
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