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 — Luxembourgite leaves light brown, Beudantite leaves yellow; luster reads submetallic on Luxembourgite and vitreous on Beudantite.
How to tell apart: Streak differs — 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
- Typical price
- n/a
Where rockhounds find luxembourgite
Classic worldwide localities
- Mullerthal, Luxembourg
Field-hunting tip
Look in sandstone fractures country — that is 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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