Ferrisymplesite is a rare secondary mineral formed by the oxidation of arsenopyrite in mineral deposits. It is typically found as small, brownish acicular or prismatic crystals and is prized primarily by advanced mineral collectors of arsenate species.
Is this ferrisymplesite?
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 ferrisymplesite with a known reference. Ferrisymplesite sits at Mohs 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: resinous.
- 4Match the color rangeCompare against the expected color range: yellow brown, resin brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: fibrous.
Often confused with
Ferrisymplesite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Ferrisymplesite leaves brown, Symplesite leaves pale bluish; luster reads resinous on Ferrisymplesite and vitreous to oily, pearly on cleavages on Symplesite.
How to tell apart: Streak differs, so Ferrisymplesite leaves brown, Vivianite leaves white, altering to dark blue, brown; luster reads resinous on Ferrisymplesite and vitreous, pearly on the cleavage, dull when earthy on Vivianite.
Often found alongside ferrisymplesite
Minerals reported to co-occur with ferrisymplesite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe³⁺₃(AsO₄)₂(OH)₃·5H₂O
- Mohs hardness
- 2.5
- Density
- 2.885 g/cm³
- Colors
- Yellow brownResin brown
- Streak
- Brown
- Luster
- Resinous
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous
- Cleavage
- Perfect on {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In the oxidized zone of a Co–Ni sulfide deposit (Hudson Bay mine, Canada); in the oxidized zone of a polymetallic hydrothermal ore deposit (Neubulach, Germany)
Where rockhounds find ferrisymplesite
Classic worldwide localities
- Hudson Bay mine, Timiskaming district, Cobalt, Ontario, Canada
- Neubulach, Black Forest, Germany
Field-hunting tip
Where it forms: In the oxidized zone of a Co–Ni sulfide deposit (Hudson Bay mine, Canada); in the oxidized zone of a polymetallic hydrothermal ore deposit (Neubulach, Germany). If you start seeing erythrite–annabergite, copper, malachite 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 ferrisymplesite?+
Where is ferrisymplesite found?+
Is ferrisymplesite safe to handle?+
What rocks look like ferrisymplesite?+
What minerals are found with ferrisymplesite?+
What kind of rock does ferrisymplesite form in?+
What is ferrisymplesite used for?+
Find ferrisymplesite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
