Holtedahlite is a rare magnesium phosphate mineral typically found as transparent to translucent tabular crystals or granular aggregates. It is primarily known from metasomatic zones within serpentinized ultramafic rocks and is a highly sought-after specimen for advanced mineral collectors.
Is this holtedahlite?
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 holtedahlite with a known reference. Holtedahlite 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. Holtedahlite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Holtedahlite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white, pale green.
- 5Look at form & habitCrystal system: trigonal. Typical habit: tabular crystals, massive, granular.
Often confused with
Holtedahlite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Ludwigite is the harder of the two (Mohs 5 vs. 4); streak differs, so Holtedahlite leaves white, Ludwigite leaves black; luster reads vitreous on Holtedahlite and submetallic on Ludwigite.
How to tell apart: Apatite is the harder of the two (Mohs 5 vs. 4).
Often found alongside holtedahlite
Minerals reported to co-occur with holtedahlite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mg₃(PO₄)(OH,F)
- Mohs hardness
- 4
- Density
- 3.08 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Tabular Crystals, Massive, Granular
- Cleavage
- Perfect On {0001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Metasomatic Rocks in Serpentinite
- Typical price
- $20-150 for small specimens
Where rockhounds find holtedahlite
Classic worldwide localities
- Modum, Buskerud, Norway
- Kola Peninsula, Russia
Field-hunting tip
Look in metasomatic rocks in serpentinite country, the host setting where holtedahlite typically forms. If you start seeing magnesite, serpentine, ludwigite in float, you are in the right ground. Field specimens usually show a tabular crystals, massive, granular habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find holtedahlite on the map
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