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 — that is 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.