Kastningite is a rare manganese aluminum phosphate mineral often found as a secondary phase in granite pegmatites. It typically occurs as small, delicate bladed or lath-like crystals exhibiting a distinctive pink to violet hue. Collectors prize it for its rarity and its beautiful, sharp crystal habit, usually found in phosphate-rich zones within complex pegmatite bodies.
Is this kastningite?
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 kastningite with a known reference. Kastningite sits at Mohs 3.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Kastningite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Kastningite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: pink, violet, reddish-pink.
- 5Look at form & habitCrystal system: triclinic. Typical habit: bladed crystals, aggregates, crusts.
Often confused with
Kastningite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside kastningite
Minerals reported to co-occur with kastningite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Mn²⁺,Fe²⁺)Al₂(PO₄)₂(OH)₂·8H₂O
- Mohs hardness
- 3.5
- Density
- 2.36 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Bladed Crystals, Aggregates, Crusts
- Cleavage
- Perfect On {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Granite Pegmatites
- Typical price
- $50-300 per specimen
Where rockhounds find kastningite
Classic worldwide localities
- Tip Top Mine, South Dakota, USA
- Mangualde, Portugal
- Hagendorf, Germany
Field-hunting tip
Look in granite pegmatites country — that is the host setting where kastningite typically forms. If you start seeing triplite, heterosite, rockbridgeite in float, you are in the right ground. Field specimens usually show a bladed crystals, aggregates, crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find kastningite on the map
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