Samuelsonite is a rare phosphate mineral primarily found in complex granite pegmatites. It typically occurs as small, pale-colored crystals or granular masses associated with other phosphate minerals, making it a prized specimen for advanced systematic mineral collectors.
Is this samuelsonite?
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 samuelsonite with a known reference. Samuelsonite sits at Mohs >5, 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: subadamantine, may be vitreous to resinous.
- 4Match the color rangeCompare against the expected color range: colorless.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic, striated.
Often confused with
Samuelsonite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads subadamantine, may be vitreous to resinous on Samuelsonite and vitreous on Apatite.
How to tell apart: Luster reads subadamantine, may be vitreous to resinous on Samuelsonite and vitreous to subresinous on Triphylite.
Often found alongside samuelsonite
Minerals reported to co-occur with samuelsonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₉Mn₄Al₂(PO₄)₁₀(OH)₂
- Mohs hardness
- >5
- Density
- 3.24-3.35 g/cm³
- Colors
- Streak
- White
- Luster
- Subadamantine, may be vitreous to resinous
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic, striated
- Cleavage
- On {001}, fair
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral in complex zoned granite pegmatites
Where rockhounds find samuelsonite
Classic worldwide localities
- Palermo #1 mine, near North Groton, Grafton Co., New Hampshire, USA
- Buranga pegmatite, near Gatumba, Rwanda
Field-hunting tip
Where it forms: A secondary mineral in complex zoned granite pegmatites. If you start seeing childrenite, hydroxylapatite, arrojadite in float, you are in the right ground. Typical habit: prismatic, striated. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify samuelsonite?+
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What rocks look like samuelsonite?+
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Find samuelsonite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
