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.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareChildrenite-Eosphorite Group family

Ernstite

Hardness: 5
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this ernstite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch ernstite with a known reference. Ernstite sits at Mohs 5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Ernstite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Ernstite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: yellow, yellow-orange, reddish-brown.
5
Look at form & habit
Crystal 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.

How to tell apart: Luster reads vitreous on Ernstite and vitreous to resinous on Childrenite.

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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
Colors: Yellow Yellow-orange Reddish-brown
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, 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

How do you identify ernstite?+

Mohs hardness is 5. It typically shows a vitreous luster. The streak is white. Common colors include yellow, yellow-orange, reddish-brown.

Where is ernstite found?+

Notable localities include Aracuai, Minas Gerais, Brazil; Hagendorf, Bavaria, Germany.

How much is ernstite worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like ernstite?+

Ernstite is most often confused with Eosphorite, Childrenite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with ernstite?+

Ernstite commonly co-occurs with Eosphorite, Triplite, Dickinsonite, Apatite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does ernstite form in?+

Ernstite typically forms in granite pegmatites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is ernstite used for?+

Ernstite is used in collector.

Find ernstite on the map

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