Ilímaussite-(Ce) is a rare silicate mineral found almost exclusively in the alkaline rocks of the Ilimaussaq complex in Greenland. It typically occurs as small, pale yellow to brownish platy crystals embedded in pegmatite matrices. Due to its radioactive content, it is highly sought after by systematic mineral collectors.
Is this ilímaussite-(ce)?
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 ilímaussite-(ce) with a known reference. Ilímaussite-(Ce) sits at Mohs ~4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: resinous.
- 4Match the color rangeCompare against the expected color range: brownish yellow, yellowish white.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: platy crystals.
Often confused with
Ilímaussite-(Ce) vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Ilímaussite-(Ce) leaves white, Steenstrupine-(Ce) leaves brownish, nearly white; luster reads resinous on Ilímaussite-(Ce) and dull on Steenstrupine-(Ce).
How to tell apart: Eudialyte is the harder of the two (Mohs 5-6 vs. ~4); luster reads resinous on Ilímaussite-(Ce) and vitreous to dull on Eudialyte.
Often found alongside ilímaussite-(ce)
Minerals reported to co-occur with ilímaussite-(ce). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Ba,Na)₁₀K₃Na₄.₅Ce₅(Nb,Ti)₆O₆(Si₁₂O₃₆)(Si₉O₁₈)(O,OH)₂₄
- Mohs hardness
- ~4
- Density
- 3.6 g/cm³
- Streak
- White
- Luster
- Resinous
- Transparency
- Transparent to translucent
- Crystal system
- Hexagonal
- Crystal habit
- Platy crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a hydrothermal ussingite-analcime vein cutting sodalite syenite in an alkalic massif
Where rockhounds find ilímaussite-(ce)
Classic worldwide localities
- Ilimaussaq alkaline complex, South Greenland (type locality)
Field-hunting tip
Where it forms: In a hydrothermal ussingite-analcime vein cutting sodalite syenite in an alkalic massif. If you start seeing chkalovite, epistolite in float, you are in the right ground. Typical habit: platy crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ilímaussite-(ce)?+
Where is ilímaussite-(ce) found?+
Is ilímaussite-(ce) safe to handle?+
What rocks look like ilímaussite-(ce)?+
What minerals are found with ilímaussite-(ce)?+
What kind of rock does ilímaussite-(ce) form in?+
What is ilímaussite-(ce) used for?+
Find ilímaussite-(ce) on the map
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