Ernstite is a rare phosphate mineral that forms through the oxidation of eosphorite in pegmatite environments. It typically occurs as prismatic crystals or radial sprays with a distinct yellowish to reddish-brown coloration, often found in association with other phosphate minerals.
Is this ernstite?
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 ernstite with a known reference. Ernstite sits at Mohs 5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Ernstite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Ernstite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, yellow-orange, reddish-brown.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: prismatic crystals, radial aggregates.
Often confused with
Ernstite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside ernstite
Minerals reported to co-occur with ernstite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Mn²⁺,Fe³⁺)Al(PO₄)(OH,O)₂·H₂O
- Mohs hardness
- 5
- Density
- 3.37 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Prismatic Crystals, Radial Aggregates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Granite Pegmatites
- Typical price
- $50-300 per specimen
Where rockhounds find ernstite
Classic worldwide localities
- Aracuai, Minas Gerais, Brazil
- Hagendorf, Bavaria, Germany
Field-hunting tip
Look in granite pegmatites country — that is the host setting where ernstite typically forms. If you start seeing eosphorite, triplite, dickinsonite in float, you are in the right ground. Field specimens usually show a prismatic crystals, radial aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find ernstite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
