Luxembourgite is an extremely rare phosphate mineral first discovered in the Mullerthal region of Luxembourg. It typically occurs as minute, dark, needle-like crystals within sandstone cavities, often requiring micro-analysis for definitive identification.
Is this luxembourgite?
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 luxembourgite with a known reference. Luxembourgite sits at Mohs 4-5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Luxembourgite leaves a light brown streak.
- 3Read the lusterHold the specimen under a strong light. Luxembourgite typically shows a submetallic luster.
- 4Match the color rangeCompare against the expected color range: dark brown, black.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: acicular crystals.
Often confused with
Luxembourgite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Luxembourgite leaves light brown, Beudantite leaves yellow; luster reads submetallic on Luxembourgite and vitreous on Beudantite.
How to tell apart: Streak differs, so Luxembourgite leaves light brown, Corkite leaves yellow; luster reads submetallic on Luxembourgite and vitreous on Corkite.
Often found alongside luxembourgite
Minerals reported to co-occur with luxembourgite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- AgPb(Al₆)(PO₄)₄(OH)₈·H₂O
- Mohs hardness
- 4-5
- Density
- 4.67 g/cm³
- Colors
- Streak
- Light Brown
- Luster
- Submetallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Acicular Crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Sandstone Fractures
Where rockhounds find luxembourgite
Classic worldwide localities
- Mullerthal, Luxembourg
Field-hunting tip
Look in sandstone fractures country, the host setting where luxembourgite typically forms. If you start seeing quartz, goethite, hematite in float, you are in the right ground. Field specimens usually show a acicular crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find luxembourgite on the map
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