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 colorless to white 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. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: colorless, white, beige.
- 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
- MnAl₂(PO₄)₂(OH)₂·8H₂O
- Mohs hardness
- 3.5
- Density
- 2.35 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Triclinic
- Crystal habit
- Bladed crystals, aggregates, crusts
- Cleavage
- Perfect on {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare secondary mineral in a zoned granite pegmatite
Where rockhounds find kastningite
Classic worldwide localities
- Silbergrube quarry, near Waidhaus, and at Hagendorf, Bavaria, Germany
- NaIIle: To honor Jiirgen Kastning, mineral collector and dealer, Reinbek, near Hamburg, Germany
Field-hunting tip
Where it forms: A rare secondary mineral in a zoned granite pegmatite. If you start seeing variscite, paravauxite, albite in float, you are in the right ground. Typical habit: bladed crystals, aggregates, crusts. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify kastningite?+
Where is kastningite found?+
What rocks look like kastningite?+
What minerals are found with kastningite?+
What kind of rock does kastningite form in?+
What is kastningite used for?+
Find kastningite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
