Triploidite is an uncommon phosphate mineral typically found in phosphate-rich zones of complex granite pegmatites. Collectors look for its characteristic yellow-to-brownish massive aggregates or small, somewhat fibrous prismatic crystals often associated with other rare phosphate species.
Is this triploidite?
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 triploidite with a known reference. Triploidite sits at Mohs 4.5-5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white, nearly.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous, adamantine, greasy.
- 4Match the color rangeCompare against the expected color range: yellow, greenish, yellow brown, pink, reddish brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: columnar, fibrous.
Often confused with
Triploidite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside triploidite
Minerals reported to co-occur with triploidite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mn₂(PO₄)(OH)
- Mohs hardness
- 4.5-5
- Density
- 3.70 g/cm³
- Streak
- White, nearly
- Luster
- Vitreous, adamantine, greasy
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Columnar, fibrous
- Cleavage
- {100}, good; {120}, fair; {010}, poor
- Rarity
- Rare
- Uses
- Collector
- Host rock
- An uncommon hydrothermal alteration product of primary phosphates in complex zoned granite pegmatites
Where rockhounds find triploidite
Classic worldwide localities
- Branchville, Fairfield Co., Connecticut, USA
- Ross (Highland Lode) mine, 6.5 km west of Custer, Custer Co. and the Peerless mine, near Keystone, Pennington Co., South Dakota, USA
- White Picacho district, Maricopa and Yavapai Cos., Arizona, USA
- Foote mine, Kings Mountain, Cleveland Co., North Carolina, USA
- Wheal Owles, St. Just, Cornwall, England
- Hunnakko pegmatite, Alavus district, Finland
Field-hunting tip
Where it forms: An uncommon hydrothermal alteration product of primary phosphates in complex zoned granite pegmatites. If you start seeing triplite, lithiophilite, triphylite in float, you are in the right ground. Typical habit: columnar, fibrous. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify triploidite?+
Where is triploidite found?+
What rocks look like triploidite?+
What minerals are found with triploidite?+
What kind of rock does triploidite form in?+
What is triploidite used for?+
Find triploidite on the map
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