Dickinsonite-(KMnNa) is a rare secondary phosphate mineral typically found in complex granite pegmatites. Collectors look for its characteristic olive-green, platy, or foliated habits that often form in cavities alongside other secondary phosphates.
Is this dickinsonite-(kmnna)?
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 dickinsonite-(kmnna) with a known reference. Dickinsonite-(KMnNa) sits at Mohs 3.5-4, 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: vitreous.
- 4Match the color rangeCompare against the expected color range: vivid green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals, foliated masses, lamellar aggregates.
Often confused with
Dickinsonite-(KMnNa) vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads vitreous on Dickinsonite-(KMnNa) and pearly to subadamantine, vitreous on the {001} cleavage on Fairfieldite.
How to tell apart: Luster reads vitreous on Dickinsonite-(KMnNa) and subresinous to greasy on Fillowite.
Often found alongside dickinsonite-(kmnna)
Minerals reported to co-occur with dickinsonite-(kmnna). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K(NaMn)CaNa₃AlMn₁₃(PO₄)₁₂(OH)₂
- Mohs hardness
- 3.5-4
- Density
- 3.496 g/cm³
- Colors
- Vivid green
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular crystals, foliated masses, lamellar aggregates
- Cleavage
- On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In nodular masses in albitic granite pegmatite
Where rockhounds find dickinsonite-(kmnna)
Classic worldwide localities
- Branchville, Fairfield County, Connecticut, USA (type locality)
Field-hunting tip
Where it forms: In nodular masses in albitic granite pegmatite. If you start seeing quartz, eosphorite, triploidite in float, you are in the right ground. Typical habit: tabular crystals, foliated masses, lamellar aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify dickinsonite-(kmnna)?+
Where is dickinsonite-(kmnna) found?+
What rocks look like dickinsonite-(kmnna)?+
What minerals are found with dickinsonite-(kmnna)?+
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Find dickinsonite-(kmnna) on the map
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