Strunzite is a rare phosphate mineral typically found as radiating clusters of delicate yellow or brown needles. It forms as a secondary mineral during the alteration of primary triphylite in granitic pegmatites. Collectors prize it for its fragile, aesthetic crystal sprays, often found tucked into vugs within phosphate-bearing ore.
Is this strunzite?
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 strunzite with a known reference. Strunzite 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. Streak: light yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: brownish yellow, golden yellow, straw yellow.
- 5Look at form & habitCrystal system: triclinic. Typical habit: acicular, lath.
Often confused with
Strunzite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Strunzite is noticeably harder (Mohs 4 vs. 3); streak differs, so Strunzite leaves light yellow, Stewartite leaves white.
How to tell apart: Strunzite is noticeably harder (Mohs 4 vs. 3); streak differs, so Strunzite leaves light yellow, Laueite leaves white.
How to tell apart: Streak differs, so Strunzite leaves light yellow, Phosphosiderite leaves white.
Often found alongside strunzite
Minerals reported to co-occur with strunzite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mn²⁺Fe³⁺₂(PO₄)₂(OH)₂·6H₂O
- Mohs hardness
- 4
- Density
- 2.52 g/cm³
- Streak
- Light yellow
- Luster
- Vitreous
- Transparency
- Semitransparent
- Crystal system
- Triclinic
- Crystal habit
- Acicular, lath
- Cleavage
- Good
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral, typically altered from triphylite, in zoned complex granite pegmatites
Where rockhounds find strunzite
Classic worldwide localities
- Palermo #1 and Fletcher mines, near North Groton, Grafton Co., the G.E. Smith mine, Newport, Sullivan Co., and the Fitzgibbon mine, Alstead, Cheshire Co., New Hampshire, USA
- Red Hill quarry, Rumford, and the BB quarry, Norway, Oxford Co., Maine, USA
- Big Chief mine, one km south of Glendale, and the Hesnard and Etta mines, near Keystone, Pennington Co., from the Tip Top mine, 8.5 km southwest of Custer, Custer Co., South Dakota, USA
- Foote mine, Kings Mountain, Cleveland Co., North Carolina, USA
- Hagendorf, Waidhaus, and Hühnerkobel, near Zwiesel, Bavaria, Germany
- Blaton, Belgium
Field-hunting tip
Where it forms: A secondary mineral, typically altered from triphylite, in zoned complex granite pegmatites. If you start seeing triphylite, laueite, rockbridgeite in float, you are in the right ground. Typical habit: acicular, lath. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify strunzite?+
Where is strunzite found?+
What rocks look like strunzite?+
What minerals are found with strunzite?+
What kind of rock does strunzite form in?+
What is strunzite used for?+
Find strunzite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
