Ferrisepiolite is a rare iron-rich member of the sepiolite group, typically presenting as fibrous, earthy masses with a yellowish to brownish color. It is usually found in hydrothermal environments where iron-rich fluids interact with magnesium-rich silicate rocks.

Hardness

Mohs

Luster

Dull

Streak

White

Transparency

Opaque

mineralrareSepiolite Group family

Ferrisepiolite

Hardness: 2
Luster: Dull
Streak: White
Transparency: Opaque

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Is this ferrisepiolite?

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 ferrisepiolite with a known reference. Ferrisepiolite 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. Ferrisepiolite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Ferrisepiolite typically shows a dull luster.
4
Match the color range
Compare against the expected color range: yellow, brown, greenish.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: fibrous.

Often confused with

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

Often found alongside ferrisepiolite

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

All properties

Chemical formula: Mg₂Fe³⁺₂Si₆O₁₆(OH)₂·6H₂O
Mohs hardness: 2
Density: 2.1-2.3 g/cm³
Colors: Yellow Brown Greenish
Streak: White
Luster: Dull
Transparency: Opaque
Crystal system: Orthorhombic
Crystal habit: Fibrous
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Hydrothermal Veins
Typical price: $20-100 per specimen

Where rockhounds find ferrisepiolite

Classic worldwide localities

Russia
Germany
Czech Republic

Field-hunting tip

Look in hydrothermal veins country, the host setting where ferrisepiolite typically forms. If you start seeing magnetite, hematite, quartz in float, you are in the right ground. Field specimens usually show a fibrous habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify ferrisepiolite?+

Mohs hardness is 2. It typically shows a dull luster. The streak is white. Common colors include yellow, brown, greenish.

Where is ferrisepiolite found?+

Notable localities include Russia; Germany; Czech Republic.

How much is ferrisepiolite worth?+

Typical asking prices fall in the range of $20-100 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like ferrisepiolite?+

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

What minerals are found with ferrisepiolite?+

Ferrisepiolite commonly co-occurs with Magnetite, Hematite, Quartz. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does ferrisepiolite form in?+

Ferrisepiolite typically forms in hydrothermal veins. Working float back to the host body is the standard way to chase a fresh occurrence.

What is ferrisepiolite used for?+

Ferrisepiolite is used in collector.

Find ferrisepiolite on the map

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