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 — 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 — that is 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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