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.
Is this ferrisepiolite?
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 ferrisepiolite with a known reference. Ferrisepiolite sits at Mohs 2-2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brown.
- 3Read the lusterHold the specimen under a strong light. Luster: non-metallic.
- 4Match the color rangeCompare against the expected color range: brown, red-brown.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: fibrous.
Often confused with
Ferrisepiolite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Ferrisepiolite leaves brown, Sepiolite leaves white; luster reads non-metallic on Ferrisepiolite and dull on Sepiolite.
How to tell apart: Streak differs, so Ferrisepiolite leaves brown, Palygorskite leaves white; luster reads non-metallic on Ferrisepiolite and earthy to waxy on Palygorskite.
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
- 2-2.5
- Density
- 2.51 g/cm³
- Streak
- Brown
- Luster
- Non-metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Fibrous
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In late-stage veinlets cutting copper-sulfide ores hosted in layered hedenbergite-andradite-actinolite-vesuvianite contact metamorphic rocks (skarns)
Where rockhounds find ferrisepiolite
Classic worldwide localities
- Saishitang copper skarn deposit, Xinghai County, Qinghai Province, China
Field-hunting tip
Where it forms: In late-stage veinlets cutting copper-sulfide ores hosted in layered hedenbergite-andradite-actinolite-vesuvianite contact metamorphic rocks (skarns). If you start seeing calcite, siderite in float, you are in the right ground. Typical habit: fibrous. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ferrisepiolite?+
Where is ferrisepiolite found?+
What rocks look like ferrisepiolite?+
What minerals are found with ferrisepiolite?+
What kind of rock does ferrisepiolite form in?+
What is ferrisepiolite used for?+
Find ferrisepiolite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
