Ferrisurite is a rare phyllosilicate mineral that typically appears as soft, fibrous, or earthy yellow masses within hydrothermal alteration zones. It is often found associated with lead-bearing mineral deposits and is primarily sought after by advanced collectors of rare species due to its scarcity.
Is this ferrisurite?
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 ferrisurite with a known reference. Ferrisurite 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: greenish yellow to olive-green.
- 3Read the lusterHold the specimen under a strong light. Luster: silky.
- 4Match the color rangeCompare against the expected color range: forest green, yellow green, olive green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: fibrous.
Often confused with
Ferrisurite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Ferrisurite leaves greenish yellow to olive-green, Nontronite leaves white; luster reads silky on Ferrisurite and waxy, resinous, dull on Nontronite.
How to tell apart: Streak differs, so Ferrisurite leaves greenish yellow to olive-green, Jarosite leaves pale yellow; luster reads silky on Ferrisurite and subadamantine to vitreous, resinous on fractures on Jarosite.
Often found alongside ferrisurite
Minerals reported to co-occur with ferrisurite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pb₂.₄Fe₂Si₄O₁₀(CO₃)₁.₇(OH)₃·nH₂O
- Mohs hardness
- 2-2.5
- Density
- 4.0 g/cm³
- Colors
- Streak
- Greenish yellow to olive-green
- Luster
- Silky
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous
- Cleavage
- Perfect on {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In an oxidized lead deposit in contact metamorphosed impure limestone, as an oxidation product of silicates proximate to galena
Where rockhounds find ferrisurite
Classic worldwide localities
- Shirley Ann claim, Ubehebe district, west of Death Valley, Inyo Co., California, USA
Field-hunting tip
Where it forms: In an oxidized lead deposit in contact metamorphosed impure limestone, as an oxidation product of silicates proximate to galena. If you start seeing galena, pyrite, chalcopyrite 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 ferrisurite?+
Where is ferrisurite found?+
Is ferrisurite safe to handle?+
What rocks look like ferrisurite?+
What minerals are found with ferrisurite?+
What kind of rock does ferrisurite form in?+
What is ferrisurite used for?+
Find ferrisurite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
