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. Triploidite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Triploidite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, yellow-brown, pink, reddish-brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: fibrous, massive, or as prismatic crystals.
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
- (Mn,Fe)₂PO₄(OH)
- Mohs hardness
- 4.5-5
- Density
- 3.7-3.9 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous, Massive, Or as Prismatic Crystals
- Cleavage
- Distinct
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Granite Pegmatites
- Typical price
- $20-150 for thumbnail to small cabinet specimens
Where rockhounds find triploidite
Classic worldwide localities
- Branchville, Connecticut, USA
- Mangualde, Portugal
- Hagendorf, Germany
- Minas Gerais, Brazil
Field-hunting tip
Look in granite pegmatites country — that is the host setting where triploidite typically forms. If you start seeing eosphorite, dickinsonite, apatite in float, you are in the right ground. Field specimens usually show a fibrous, massive, or as prismatic crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify triploidite?+
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Find triploidite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
