Rokühnite is a very rare iron chloride hydrate that typically forms as a secondary mineral in oxidized iron-ore deposits. Because it is highly deliquescent and sensitive to humidity, it must be stored in a sealed, dry environment to prevent it from absorbing moisture and dissolving.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Rokühnite

Hardness: 2
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this rokühnite?

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 rokühnite with a known reference. Rokühnite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Rokühnite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Rokühnite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: yellow, pale green.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: tabular crystals, crusts.

Often confused with

Rokühnite vs. its common look-alikes, and how to tell them apart in the field.

How to tell apart: Streak differs, so Rokühnite leaves white, Erythrite leaves pale pink; luster reads vitreous on Rokühnite and adamantine to pearly on Erythrite.

Compare →

Often found alongside rokühnite

Minerals reported to co-occur with rokühnite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: FeCl₂·2H₂O
Mohs hardness: 2
Density: 2.33 g/cm³
Colors: Yellow Pale Green
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Tabular Crystals, Crusts
Cleavage: Distinct
Rarity: Rare
Uses: Collector
Host rock: Oxidized Hydrothermal Iron Deposits
Typical price: $50-300 per specimen

Where rockhounds find rokühnite

Classic worldwide localities

Kopparberg, Sweden
Saxony, Germany

Field-hunting tip

Look in oxidized hydrothermal iron deposits country, the host setting where rokühnite typically forms. If you start seeing hematite, goethite, lawrencite in float, you are in the right ground. Field specimens usually show a tabular crystals, crusts habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify rokühnite?+

Mohs hardness is 2. It typically shows a vitreous luster. The streak is white. Common colors include yellow, pale green.

Where is rokühnite found?+

Notable localities include Kopparberg, Sweden; Saxony, Germany.

How much is rokühnite 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 rokühnite?+

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

What minerals are found with rokühnite?+

Rokühnite commonly co-occurs with Hematite, Goethite, Lawrencite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does rokühnite form in?+

Rokühnite typically forms in oxidized hydrothermal iron deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is rokühnite used for?+

Rokühnite is used in collector.

Find rokühnite on the map

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