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, 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
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
